Primary clutch electronic CVT

ABSTRACT

A continuously variable transmission (CVT) is provided for use on a recreational or utility vehicle. The CVT is electronically controlled by at least one control unit of the vehicle. The CVT includes a primary clutch having a first sheave and a second sheave moveable relative to the first sheave. An actuator controls movement of the second sheave.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/547,485, titled “Primary Clutch Electronic CVT,”filed Oct. 14, 2011, the disclosure of which is expressly incorporatedby reference herein.

FIELD OF THE DISCLOSURE

The present disclosure relates to electronically controlledtransmissions, and more particularly to systems and methods forcontrolling an electronically controlled continuously variabletransmission (CVT) for recreational and utility vehicles.

BACKGROUND AND SUMMARY

Some recreational vehicles, such as all-terrain vehicles (ATV's),utility vehicles, motorcycles, etc., include a continuously variabletransmission (CVT). In these vehicles, an actuator adjusts the positionof one of the primary and secondary clutches of the CVT. The thrustrequirement of the actuator for moving the clutch is generally dependenton the sliding friction between the movable sheave and the slidingcoupling.

Available space is often limited around the CVT for placing thecomponents of the actuator assembly. As such, actuator components havinga large package size are often difficult to place in close proximity tothe CVT. Further, the removal of some or all of the actuator componentsis often required when replacing the CVT belt.

A starting clutch is sometimes used to engage the CVT. The startingclutch is positioned at the driven or secondary clutch of the CVT toengage the secondary clutch when the CVT is in a low gear ratiocondition. Due to the low speeds and high torques of the secondaryclutch when the starting clutch engages the secondary clutch, thestarting clutch is generally large in size.

In some recreational vehicles with CVT's, such as snowmobiles, theelectrical system does not include a battery. As such, the rotationalmotion of the engine is used to generate power for the vehicle. In thesevehicles, or in vehicles that experience a sudden power loss, the clutchassembly of the CVT may require a manual reset to a home position priorto starting the vehicle.

In an exemplary embodiment of the present disclosure, a recreationalvehicle is provided including a chassis and a drive train. The drivetrain includes an engine supported by the chassis, a continuouslyvariable transmission driven by the engine, and a ground engagingmechanism configured to support the chassis. The continuously variabletransmission includes a first clutch and a second clutch. The firstclutch is adjustable to modulate a gear ratio of the continuouslyvariable transmission. The vehicle includes a suspension system coupledbetween the chassis and the ground engaging mechanism. The vehiclefurther includes at least one of a speed sensor and a suspension sensor.The speed sensor is configured to detect a speed of the drive train, andthe suspension sensor is configured to detect a height of the suspensionsystem. The vehicle further includes a controller configured to controlthe first clutch of the continuously variable transmission. Thecontroller is operative to detect an airborne state of the vehicle basedon at least one of the detected speed of the drive train and thedetected height of the suspension system. The controller is operative toadjust the first clutch upon a detection of the airborne state to reducean acceleration of the drive train.

In another exemplary embodiment of the present disclosure, a method ofcontrolling a continuously variable transmission of a vehicle isprovided. The method includes providing a vehicle including a chassis, asuspension system, and a drive train. The drive train includes anengine, a continuously variable transmission driven by the engine, and aground engaging mechanism configured to support the chassis. Thecontinuously variable transmission includes a first clutch and a secondclutch. The first clutch is adjustable to modulate a gear ratio of thecontinuously variable transmission. The method includes detecting aspeed of the drive train with a speed sensor and detecting an airbornestate of the vehicle based on at least one of an acceleration of thedrive train and a height of the suspension system. The acceleration isdetermined based on the detected speed of the vehicle. The methodfurther includes adjusting the first clutch of the continuously variabletransmission upon detection of the airborne state of the vehicle toreduce the acceleration of the drive train.

In yet another exemplary embodiment of the present disclosure, a methodof controlling a continuously variable transmission of a vehicle isprovided. The method includes providing a vehicle having a continuouslyvariable transmission, an actuator coupled to the continuously variabletransmission, and an auxiliary power connector configured to routeelectrical power from an external power supply to the actuator. Thecontinuously variable transmission includes a first clutch, a secondclutch, and a belt coupled to the first and second clutches. Theactuator is configured to move the first clutch to adjust a gear ratioof the continuously variable transmission. The method includes detectinga connection of the external power supply to the auxiliary powerconnector. The method further includes routing to the actuatorelectrical power from the auxiliary power connector upon detecting theexternal power supply. The method further includes controlling theactuator with the electrical power to move the first clutch to a homeposition.

In still another exemplary embodiment of the present disclosure, arecreational vehicle is provided including a chassis and a drive train.The drive train includes an engine supported by the chassis, acontinuously variable transmission driven by the engine, and a groundengaging mechanism configured to support the chassis. The continuouslyvariable transmission includes a first clutch, a second clutch, and abelt coupled to the first and second clutches. The first clutch isadjustable to modulate a gear ratio of the continuously variabletransmission. The vehicle further includes an actuator coupled to thecontinuously variable transmission for adjusting the first clutch. Thevehicle further includes an auxiliary power connector configured toroute electrical power to the actuator from an external power source.The vehicle further includes a controller operative to control routingof the electrical power from the external power source to the actuatorto power the actuator. The controller is operative to detect aconnection of the external power source to the auxiliary power connectorand to control the actuator with the electrical power to move the firstclutch to a home position upon detection of the external power supply.

In another exemplary embodiment of the present disclosure, a method ofcontrolling a continuously variable transmission of a vehicle isprovided. The method includes providing a vehicle having a continuouslyvariable transmission, an actuator coupled to the continuously variabletransmission, a power generator configured to provide electrical powerto the vehicle during operation of the vehicle, and an energy storagedevice. The continuously variable transmission includes a first clutchand a second clutch. The actuator is configured to adjust a position ofthe first clutch to modulate a gear ratio of the continuously variabletransmission. The method includes controlling the first clutch of thecontinuously variable transmission with the electrical power providedwith the power generator. The method further includes charging theenergy storage device with the electrical power provided with the powergenerator during operation of the vehicle while the energy storagedevice is electrically decoupled from the actuator. The method furtherincludes detecting a loss of electrical power from the power generator.The method further includes routing electrical power from the energystorage device to the actuator to move the first clutch to a homeposition upon detecting the loss of electrical power from the powergenerator.

In yet another exemplary embodiment of the present disclosure, arecreational vehicle is provided that includes a chassis and a drivetrain. The drive train includes an engine supported by the chassis, acontinuously variable transmission driven by the engine, and a groundengaging mechanism configured to support the chassis. The continuouslyvariable transmission includes a first clutch, a second clutch, and abelt coupled to the first and second clutches. The first clutch isadjustable to modulate a gear ratio of the continuously variabletransmission. The vehicle includes a power generator coupled to anddriven by the engine for providing electrical power to the vehicle. Thevehicle includes an energy storage device configured to store electricalpower provided by the power generator. The vehicle further includes atleast one controller operative to route power from the power generatorto the actuator to control the position of first clutch of thecontinuously variable transmission during vehicle operation. The atleast one controller is further operative to route electrical powerstored at the energy storage device to the actuator to move the firstclutch to a home position upon detection by the at least one controllerof a loss of electrical power from the power generator.

In still another exemplary embodiment of the present disclosure, amethod of controlling a continuously variable transmission of a vehicleis provided. The vehicle includes an engine operative to drive thecontinuously variable transmission. The continuously variabletransmission of the vehicle includes a first clutch and a second clutch.The first clutch is moveable by an actuator to modulate a gear ratio ofthe continuously variable transmission. The method includes determininga speed of the engine of the vehicle, detecting a throttle demand, anddetermining a clutch control variable based on an operator input device.The method includes calculating a target engine speed based on thethrottle demand and the clutch control variable. The method furtherincludes calculating a target position of the first clutch of thecontinuously variable transmission based on the calculated target enginespeed and the determined speed of the engine.

In another exemplary embodiment of the present disclosure, a vehicle isprovided that includes a chassis, a ground engaging mechanism configuredto support the chassis, an engine supported by the chassis, and acontinuously variable transmission driven by the engine. Thecontinuously variable transmission includes a first clutch, a secondclutch, and a belt coupled to the first and second clutches. The firstclutch is adjustable with an actuator to modulate a gear ratio of thecontinuously variable transmission. The vehicle includes a throttlevalve configured to regulate a speed of the engine. The vehicle includesat least one controller including engine control logic operative tocontrol a position of the throttle valve and transmission control logicoperative to control a position of the first clutch of the continuouslyvariable transmission. The vehicle further includes an engine speedsensor in communication with the at least one controller for detecting aspeed of the engine. The vehicle further includes a throttle operatordevice moveable by an operator. The throttle operator device includes aposition sensor in communication with the at least one controller, andthe position sensor is configured to detect a position of the throttleoperator. The vehicle further includes an operator input device incommunication with the at least one controller and configured to adjusta clutch control variable provided to the at least one controller. Thetransmission control logic is operative to calculate a target enginespeed based on the clutch control variable and the position of thethrottle operator device. The transmission control logic is operative tocalculate a target position of the first clutch of the continuouslyvariable transmission based on the target engine speed and the detectedengine speed.

In yet another exemplary embodiment of the present disclosure, a methodof controlling a continuously variable transmission of a vehicle isprovided. The vehicle includes an engine operative to drive thecontinuously variable transmission. The method includes controlling, bytransmission control logic, a first clutch of the continuously variabletransmission of the vehicle to an initial fixed position in a manualmode of operation. The continuously variable transmission includes thefirst clutch, a second clutch, and a belt coupled to the first andsecond clutches. The first clutch is adjustable to modulate a gear ratioof the continuously variable transmission. The first clutch of thecontinuously variable transmission in the manual mode of operation isadjustable between a plurality of discrete fixed positions based onshift requests initiated with a shift request device. The method furtherincludes receiving a shift request identifying a target fixed positionof the first clutch of the continuously variable transmission. Themethod further includes shifting the continuously variable transmissionfrom the initial fixed position to the target fixed position. The methodfurther includes initiating a torque reduction of the engine during theshifting to reduce a torque generated by the engine. At least one of amagnitude and a duration of the torque reduction is adjustable based onan operator input device.

In still another exemplary embodiment of the present disclosure, avehicle is provided that includes a chassis, a ground engaging mechanismconfigured to support the chassis, an engine supported by the chassis,and a continuously variable transmission driven by the engine. Thecontinuously variable transmission includes a first clutch, a secondclutch, and a belt coupled to the first and second clutches. The firstclutch is adjustable to modulate a gear ratio of the continuouslyvariable transmission. The vehicle further includes at least onecontroller configured to control a position of the first clutch of thecontinuously variable transmission in a manual mode of operation. Thevehicle further includes a shift request device in communication withthe at least one controller. In the manual mode of operation, the firstclutch of the continuously variable transmission is shifted by the atleast one controller between a plurality of discrete fixed positionsbased on shift requests initiated with the shift request device. Thevehicle further includes an operator input device in communication withthe at least one controller. The at least one controller is operative toinitiate a torque reduction of the engine during a shift of the firstclutch of the continuously variable transmission from an initial fixedposition to a target fixed position. At least one of a magnitude and aduration of the torque reduction is adjustable based on the operatorinput device.

In another exemplary embodiment of the present disclosure, a method ofcontrolling a continuously variable transmission of a vehicle isprovided. The vehicle includes an engine operative to drive thecontinuously variable transmission. The method includes controlling, bytransmission control logic, the continuously variable transmission ofthe vehicle in a manual mode of operation. In the manual mode ofoperation, a plurality of indicated gears are selectable by thetransmission control logic based on shift requests initiated with ashift request device. The plurality of indicated gears correspond to aplurality of fixed gear ratios of the continuously variable transmissionand to at least one variable gear ratio of the continuously variabletransmission. The method includes receiving a first shift requestidentifying an initial indicated gear of the plurality of indicatedgears. The method further includes varying the gear ratio of thecontinuously variable transmission across a predetermined range of gearratios based on the initial indicated gear identified with the firstshift request. The method further includes receiving a second shiftrequest identifying a different indicated gear of the plurality ofindicated gears. The method further includes controlling thecontinuously variable transmission to a fixed gear ratio upon receipt ofthe second shift request based on the different indicated gearidentified with the second shift request.

In yet another exemplary embodiment of the present disclosure, a vehicleis provided including a chassis, a ground engaging mechanism configuredto support the chassis, an engine supported by the chassis, and acontinuously variable transmission driven by the engine. Thecontinuously variable transmission includes a first clutch, a secondclutch, and a belt coupled to the first and second clutches. The firstclutch is adjustable to modulate a gear ratio of the continuouslyvariable transmission. The vehicle further includes at least onecontroller configured to control the gear ratio of the continuouslyvariable transmission in a manual mode of operation. The vehicle furtherincludes a shift request device in communication with the at least onecontroller. In the manual mode of operation, a plurality of indicatedgears are selectable by the at least one controller based on shiftrequests initiated with the shift request device. The plurality ofindicated gears correspond to a plurality of fixed gear ratios of thecontinuously variable transmission and to at least one variable gearratio of the continuously variable transmission. Upon selection of aninitial indicated gear of the plurality of indicated gears, the at leastone controller is operative to vary the gear ratio of the continuouslyvariable transmission across a predetermined range of gear ratios. Theat least one controller is operative to control the continuouslyvariable transmission to a fixed gear ratio upon receipt of a shiftrequest identifying a different indicated gear of the plurality ofindicated gears.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary vehicle incorporating theelectronic CVT of the present disclosure;

FIG. 2 is a perspective view of an exemplary drive system of the vehicleof FIG. 1 including a continuously variable transmission (CVT);

FIGS. 3a and 3b are diagrammatic views of the CVT of FIG. 2 according toone embodiment;

FIG. 4 is a front perspective view of an exemplary CVT of the vehicle ofFIG. 1 according to one embodiment including a housing with a cover anda mounting bracket;

FIG. 5 is a front perspective view of the CVT of FIG. 4 with the coverremoved from the mounting bracket;

FIG. 6 is a side view of a primary clutch of the CVT of FIG. 4;

FIG. 7 is a rear perspective view of the CVT of FIG. 4 illustrating anactuator assembly;

FIG. 8 is a front perspective view of the CVT of FIG. 4 illustrating amoveable sheave of the primary clutch in an open position;

FIG. 9 is a front perspective view of the CVT of FIG. 4 illustrating themoveable sheave of the primary clutch in a closed position;

FIG. 10 is an exploded front perspective view of the actuator assemblyof FIG. 7 with the mounting bracket partially cut away;

FIG. 11 is an exploded rear perspective view of the actuator assembly ofFIG. 7 with the mounting bracket partially cut away;

FIG. 12 is an exploded front perspective view of the primary clutch ofFIG. 6 and a launch clutch;

FIG. 13 is an exploded rear perspective view of the primary clutch ofFIG. 6 and the launch clutch of FIG. 12;

FIG. 14 is a cross-sectional view of the primary clutch of FIG. 6 takenalong line 14-14 of FIG. 8;

FIG. 15 is a cross-sectional view of the primary clutch of FIG. 6 takenalong line 15-15 of FIG. 9;

FIG. 16 is a perspective view of the primary clutch of FIG. 14illustrating the cross-section taken along line 14-14 of FIG. 8;

FIG. 17 is a perspective view of the primary clutch of FIG. 6 partiallycut away illustrating a sliding interface of the moveable sheave;

FIG. 18 is a partially exploded front perspective view of the primaryclutch and the launch clutch of FIG. 12;

FIG. 19 is a partially exploded rear perspective view of the primaryclutch and the launch clutch of FIG. 12;

FIG. 20 is a diagrammatic view of an exemplary electro-hydraulic circuitfor controlling the CVT of FIG. 2 according to one embodiment;

FIG. 21 is a block diagram illustrating an exemplary control strategyfor moving a clutch of the CVT of FIG. 2 to a home position;

FIG. 22 is a diagrammatic view of an exemplary control system of thevehicle of FIG. 1 without a system battery;

FIG. 23 is a block diagram illustrating an exemplary control strategy ofthe control system of FIG. 22 for moving a clutch of the CVT of FIG. 2to a home position;

FIG. 24 is a block diagram illustrating an exemplary method forcalculating a target position of the primary clutch of FIG. 6;

FIG. 25 illustrates an exemplary input device for adjusting a clutchcontrol variable used in the selection of a drive profile of the vehicleof FIG. 1;

FIG. 26 is an exemplary graph illustrating the clutch control variableas a function of signal output from the input device of FIG. 25;

FIG. 27 is a graph illustrating an exemplary target engine speed mapbased on throttle demand;

FIG. 28 is a graph illustrating an exemplary target clutch velocity as afunction of vehicle acceleration for calculating the target clutchposition;

FIG. 29 is a block diagram illustrating an exemplary method forcalculating a control signal provided to the actuator assembly of FIG. 7for controlling the position of the primary clutch of FIG. 6;

FIG. 30 is a graph illustrating an exemplary applied voltage limit forthe motor of FIG. 2 based on the position of the primary clutch;

FIG. 31 is a graph illustrating an exemplary maximum available enginetorque as a function of time for interrupting engine torque during agearshift in the manual operating mode of the CVT of FIG. 2;

FIG. 32 is a graph illustrating an exemplary shifting scheme for astandard manual transmission;

FIG. 33 is a graph illustrating an exemplary shifting scheme for the CVTof FIG. 2 operating in the manual mode; and

FIG. 34 is a block diagram illustrating an exemplary method fortransitioning between automatic and manual operating modes of the CVT ofFIG. 2 during vehicle operation.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplification set out hereinillustrates embodiments of the invention, and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE DRAWINGS

The embodiments disclosed herein are not intended to be exhaustive orlimit the disclosure to the precise forms disclosed in the followingdetailed description. Rather, the embodiments are chosen and describedso that others skilled in the art may utilize their teachings.

The term “logic” or “control logic” as used herein may include softwareand/or firmware executing on one or more programmable processors,application-specific integrated circuits (ASICs), field-programmablegate arrays (FPGAs), digital signal processors (DSPs), hardwired logic,or combinations thereof. Therefore, in accordance with the embodiments,various logic may be implemented in any appropriate fashion and wouldremain in accordance with the embodiments herein disclosed.

Referring initially to FIG. 1, an exemplary vehicle 10 having anelectronically controlled CVT is illustrated. Vehicle 10 isillustratively a side-by-side ATV 10 including a front end 12, a rearend 14, and a frame or chassis 15 that is supported above the groundsurface by a pair of front tires 22 a and wheels 24 a and a pair of reartires 22 b and wheels 24 b. ATV 10 includes a pair of laterallyspaced-apart bucket seats 18 a, 18 b, although a bench style seat or anyother style of seating structure may be used. Seats 18 a, 18 b arepositioned within a cab 17 of ATV 10. A protective cage 16 extends overcab 17 to reduce the likelihood of injury to passengers of ATV 10 frompassing branches or tree limbs and to act as a support in the event of avehicle rollover. Cab 17 also includes front dashboard 31, adjustablesteering wheel 28, and shift lever 29. Front dashboard 31 may include atachometer, speedometer, or any other suitable instrument.

Front end 12 of ATV 10 includes a hood 32 and a front suspensionassembly 26. Front suspension assembly 26 pivotally couples front wheels24 to ATV 10. Rear end 14 of ATV 10 includes an engine cover 19 whichextends over an engine and transmission assembly (see FIG. 2). Rear end14 further includes a rear suspension assembly (not shown) pivotallycoupling rear wheels 24 to ATV 10. Other suitable vehicles may beprovided that incorporate the CVT of the present disclosure, such as asnowmobile, a straddle-seat vehicle, a utility vehicle, a motorcycle,and other recreational and non-recreational vehicles.

Referring to FIG. 2, an exemplary drive system 40 of vehicle 10 of FIG.1 is illustrated including an engine 42 and a CVT 48. CVT 48 includes aprimary or drive clutch 50 and a secondary or driven clutch 52. Anendless, variable speed belt 54 is coupled to the primary and secondaryclutches 50, 52. Engine 42 includes an engine case or housing 43 and anoutput shaft 44 configured to drive primary clutch 50 of the CVT 48.Rotation of primary clutch 50 is transferred to secondary clutch 52 viabelt 54. An output shaft 46 of secondary clutch 52 is coupled to anddrives a sub-transmission 56 which is coupled to the final drive 58 fordriving wheels 24 (see FIG. 1). In one embodiment, sub-transmission 56is geared to provide a high gear, a low gear, a reverse gear, and a parkconfiguration for vehicle 10 of FIG. 1. Fewer or additional gears may beprovided with sub-transmission 56.

A controller 36 of drive system 40 is operative to control CVT 48 andengine 42, as described herein. Controller 36 includes at least oneprocessor 38 that executes software and/or firmware stored in memory 39of controller 36. The software/firmware code contains instructions that,when executed by processor 38, causes controller 36 to perform thefunctions described herein. Controller 36 may alternatively include oneor more application-specific integrated circuits (ASICs),field-programmable gate arrays (FPGAs), digital signal processors(DSPs), hardwired logic, or combinations thereof. The at least oneprocessor 38 of controller 36 illustratively includes engine controllogic 34 operative to control engine 42 and CVT control logic 35operative to control CVT 48. Controller 36 may be a single control unitor multiple control units functioning together to perform the functionsof controller 36 described herein. Engine control logic 34 and CVTcontrol logic 35 may be provided on a same processing device ordifferent processing devices. For example, CVT control logic 35 may beprovided on a designated clutch control unit physically separate fromand in communication with an engine control unit (ECU) of vehicle 10that contains engine control logic 34.

Memory 39 is any suitable computer readable medium that is accessible byprocessor 38. Memory 39 may be a single storage device or multiplestorage devices, may be located internally or externally to controller36, and may include both volatile and non-volatile media. Exemplarymemory 39 includes random-access memory (RAM), read-only memory (ROM),electrically erasable programmable ROM (EEPROM), flash memory, CD-ROM,Digital Versatile Disk (DVD) or other optical disk storage, a magneticstorage device, or any other suitable medium which is configured tostore data and which is accessible by controller 36.

CVT control logic 35 is operative to control an actuator assembly 80 forcontrolling the position of primary clutch 50 and thus the gear ratio ofCVT 48, as described herein. In particular, actuator assembly 80includes a motor 76 controlled by CVT control logic 35 that movesprimary clutch 50. In an exemplary embodiment, motor 76 is an electricalstepper motor, although motor 76 may alternatively be a brushed motor orother suitable electrical or hydraulic motor. In one embodiment,actuator assembly 80 and/or controller 36 includes a motor drive thatcontrols motor 76 based on control signals provided with CVT controllogic 35. Alternatively, CVT control logic 35 may control a relay forselectively routing power to motor 76 for controlling motor 76.

In the illustrated embodiment, a throttle operator 116 including aposition sensor is coupled to controller 36, and engine control logic 34electronically controls the position of a throttle valve 117 of engine42 based on the detected position of throttle operator 116 to regulateair intake to and thus the speed of engine 42. Throttle operator 116 mayinclude an accelerator pedal, a thumb actuated lever, or any othersuitable operator input device that, when actuated by an operator, isconfigured to provide an operator throttle demand to controller 36. Oneor more suspension sensors 119 provide feedback to controller 36indicative of a suspension (e.g., compression) height of the vehiclesuspension system. A display 53 is coupled to controller 36 fordisplaying vehicle operation information to an operator. Exemplaryinformation provided on display 53 includes vehicle speed, engine speed,fuel level, clutch position or gear ratio, selected operation mode(e.g., auto, manual, hydrostatic), indicated gear in manual mode, etc.Vehicle 10 further includes one or more shifters 55 for shifting betweendiscrete gear ratios when vehicle 10 operates in manual mimic mode, asdescribed herein. Speed sensors 59 provide signals to controller 36representative of an engine speed, a vehicle (ground) speed, arotational speed of primary clutch 50 and/or secondary clutch 52, and/ora speed of other components of the vehicle drive train. In oneembodiment, controller 36 communicates with one or more sensors/devicesof vehicle 10 and/or other vehicle controllers via controller areanetwork (CAN) communication.

One or more mode selection devices 113 in communication with controller36 are used by an operator to select an operating mode of vehicle 10.Exemplary operating modes include an automatic mode, a manual mimicmode, and a hydrostatic mode. In one embodiment, vehicle 10 furtherincludes a cruise switch for selecting a cruise control mode. Further,an input device 111 is used to select a drive profile (i.e., targetengine speed curve) of vehicle 10 in the automatic mode to adjustvehicle operating characteristics to range from economic operation withimproved fuel economy to sport operation with increased vehicleperformance (e.g., torque, acceleration, etc.), as described herein. Inthe illustrated embodiment, input device 111 is further used to adjust ashift intensity associated with a gear shift in the manual mimic mode,as described herein. An exemplary input device 111 is illustrated inFIG. 25 and described herein.

In the illustrated embodiment, secondary clutch 52 is a mechanicallycontrolled clutch 52 and includes a stationary sheave and a moveablesheave (not shown). Secondary clutch 52 is configured to control thetension of belt 54 of CVT 48 as primary clutch 50 is adjusted. In oneembodiment, secondary clutch 52 includes a spring and a torque-sensinghelix (not shown). The helix applies a clamping force on belt 54proportional to the torque on secondary clutch 52. The spring applies aload proportional to the displacement of the moveable sheave. In oneembodiment, secondary clutch 52 provides mechanical load feedback forCVT 48. In an alternative embodiment, controller 36 and actuatorassembly 80 may further control secondary clutch 52 of CVT 48.

As illustrated in FIGS. 3A and 3B, primary clutch 50 is coupled to androtates with a shaft 70, and secondary clutch 52 is coupled to androtates with a shaft 72. Shaft 70 is driven by the output shaft 44 ofengine 42 (see FIG. 2). Shaft 72 of secondary clutch 52 drivessub-transmission 56 (see FIG. 2). Belt 54 wraps around the primary andsecondary clutches 50, 52 and transfers rotational motion of primaryclutch 50 to secondary clutch 52.

Referring to FIG. 4, a housing 60 for CVT 48 is illustrated with a cover61 coupled to a back plate or mounting bracket 62. Flanged portions 64a, 64 b of mounting bracket 62 and cover 61, respectively, areillustratively configured to receive fasteners 74 (see FIG. 7) to couplecover 61 to mounting bracket 62. Fasteners 74 are illustratively boltsor screws, although other suitable fasteners 74 may be used. Cover 61includes a pipe portion 68 forming an opening 69 to provide access tobelt 54 of CVT 48. For example, opening 69 may be used to visuallyinspect belt 54 and/or secondary clutch 52 (see FIG. 2) or to check thetension of belt 54. Mounting bracket 62 includes a vent structure 66including a pair of vents 67 a, 67 b extending into the interior ofhousing 60 (see FIG. 5). Vents 67 a, 67 b and opening 69 cooperate toprovide airflow to CVT 48 to reduce the likelihood of the components ofCVT 48 overheating. Vent structure 66 is illustratively coupled tomounting bracket 62 via fasteners 75 (see FIG. 7), although ventstructure 66 may alternatively be integrally formed with mountingbracket 62 or cover 61. Cover 61 is removable from mounting bracket 62upon removing fasteners 74 from flanged portions 64 a, 64 b. Asillustrated in FIG. 5, cover 61 is adapted to be pulled away frommounting bracket 62 in a direction substantially perpendicular to thesurface of mounting bracket 62.

Referring to FIG. 5, primary clutch 50 of CVT 48 is secured to mountingbracket 62 via a bracket 90. Bracket 90 includes flanged portions 94each adapted to receive a fastener (not shown) to couple bracket 90 tomounting bracket 62. Bracket 90 illustratively includes an end wall 96and a curved wall 98 (see FIG. 10) that extends perpendicularly betweenend wall 96 and mounting bracket 62. In the illustrated embodiment,curved wall 98 extends partially around the outer circumference ofprimary clutch 50. A pair of posts 92 further support bracket 90 betweenend wall 96 and mounting bracket 62. Posts 92 are illustratively pressfit between flanged portions 99 of end wall 96 and mounting bracket 62,although posts 92 may alternatively be coupled to end wall 96 and/ormounting bracket 62 with fasteners. A position sensor 114 is coupled toa flange 115 (see FIG. 11) of bracket 90 for detecting the axiallocation of a moveable sheave 102 of primary clutch 50. In oneembodiment, position sensor 114 is a rotary sensor with a bell crank,although a linear sensor or other suitable sensor may be provided.Sensor 114 provides position feedback to controller 36 (FIG. 2).

As illustrated in FIG. 5, primary clutch 50 includes a pair of sheaves100, 102 that are supported by and rotate with shaft 70. Sheaves 100,102 cooperate to define a pulley or slot 104 within which belt 54 (seeFIG. 2) rides. As illustrated in FIG. 6, slot 104 is substantiallyV-shaped due to slanted inner surfaces 110, 112 of respective sheaves100, 102. Accordingly, belt 54 has a substantially V-shapedcross-section to cooperate with inner surfaces 110, 112 of the sheaves100, 102. Primary clutch 50 further includes a screw assembly includingan outer screw assembly 120 and an inner screw assembly 122 positionedbetween outer screw assembly 120 and moveable sheave 102.

In the illustrated embodiment, sheave 100 is stationary axially in adirection parallel to the axis of shaft 70, and sheave 102 is movableaxially in a direction parallel to the axis of shaft 70. In particular,sheave 102 is configured to slide along shaft 70 to a plurality ofpositions between a fully extended or open position (see FIGS. 8 and 14)and a fully closed or retracted position (see FIGS. 9 and 15). Withmoveable sheave 102 in a fully extended or open position, slot 104 is ata maximum axial width, and belt 54 rides near the radial center ofprimary clutch 50, as illustrated in FIG. 14. In the illustratedembodiment, belt 54 does not contact a tube portion 216 of a slidingsupport 200 of primary clutch 50 when moveable sheave 102 is at thefully open position of FIG. 14. With moveable sheave 102 in a fullyretracted or closed position, slot 104 is at a minimum axial width, andbelt 54 rides near the outer periphery of primary clutch 50, asillustrated in FIG. 15. Secondary clutch 52 (see FIG. 2) is similarlyconfigured with a pair of sheaves (not shown) supported by and rotatablewith shaft 72. One sheave of secondary clutch 52 is axially movable, andthe other sheave is axially stationary. In one embodiment, secondaryclutch 52 is configured to control the tension of belt 54. For purposesof illustrating primary clutch 50, secondary clutch 52 and belt 54 arenot shown in FIGS. 5, 8, and 9.

Movement of sheave 102 of primary clutch 50 and movement of the moveablesheave of secondary clutch 52 provides variable effective gear ratios ofCVT 48. In one embodiment, CVT 48 is configured to provide an infinitenumber of effective gear ratios between minimum and maximum gear ratiosbased on the positions of the moveable sheaves of the clutches 50, 52.In the configuration illustrated in FIG. 3A, the moveable sheave 102(see FIG. 6) of primary clutch 50 is substantially opened, and themoveable sheave (not shown) of secondary clutch 52 is substantiallyretracted. Accordingly, a low gear ratio is provided by CVT 48 in theconfiguration of FIG. 3A such that shaft 72 of secondary clutch 52rotates slower than shaft 70 of primary clutch 50. Similarly, in theconfiguration illustrated in FIG. 3B, the moveable sheave 102 (see FIG.6) of primary clutch 50 is substantially retracted, and the moveablesheave (not shown) of secondary clutch 52 is substantially opened.Accordingly, a high gear ratio is provided by CVT 48 in theconfiguration of FIG. 3B such that shaft 72 of secondary clutch 52rotates faster than shaft 70 of primary clutch 50.

As illustrated in FIG. 7, actuator assembly 80 is coupled to the back ofmounting bracket 62. Actuator assembly 80 is configured to move themoveable sheave 102 (see FIG. 5) of primary clutch 50, as describedherein. In the illustrative embodiment, engine 42 and sub-transmission56 (see FIG. 2) are configured to be positioned adjacent the back ofmounting bracket 62 on either side of actuator assembly 80. Inparticular, engine 42 is positioned to the right of actuator assembly 80(as viewed from FIG. 7), and the output of engine 42 couples to shaft 70of primary clutch 50 through an opening 82 of mounting bracket 62.Similarly, sub-transmission 56 is positioned to the left of actuatorassembly 80 (as viewed from FIG. 7), and shaft 72 of secondary clutch 52(see FIG. 3A) extends through an opening 84 of mounting bracket 62 todrive sub-transmission 56.

As illustrated in FIGS. 10 and 11, actuator assembly 80 includes motor76 with a geared output shaft 132, a reduction gear 130 housed within agear housing 78, and a main gear drive 86 extending outwardly from thefront of mounting bracket 62. Reduction gear 130 includes first andsecond gears 134, 136 coupled to a shaft 135. First gear 134 engagesgeared output shaft 132 of motor 76, and second gear 136 engages a firstgear 106 coupled to an end of a shaft 109 of main gear drive 86. Maingear drive 86 further includes a second gear 108 coupled to an end ofshaft 109 opposite first gear 106. Second gear 108 engages an outer gear126 of screw assembly 120 (see FIG. 6) of primary clutch 50.

Gear housing 78 includes flange portions 156 each configured to receivea fastener 158 (see FIG. 7) for coupling gear housing 78 to the back ofmounting bracket 62. Gear housing 78 includes a first portion 150, asecond or intermediate portion 152, and a third portion 154. Firstportion 150 includes an opening 151 (see FIG. 11) that receives outputshaft 132 of motor 76. Second portion 152 includes an opening 153 (seeFIG. 10) that receives reduction gear 130. Reduction gear 130 issupported at one end by second portion 152 and at the other end by asupport member 140 mounted on the front face of mounting bracket 62.Bearings 142, 146 are positioned at opposite ends of shaft 135 tofacilitate rotation of reduction gear 130 within second portion 152 andsupport member 140, respectively. Third portion 154 of housing 78 housesa portion of first gear 106 and supports the end of shaft 109 adjacentfirst gear 106. Similarly, end wall 96 of bracket 90 supports the otherend of shaft 109 adjacent second gear 108. As illustrated in FIG. 11,bearings 144, 148 are coupled at opposite ends of shaft 109 tofacilitate rotation of main gear drive 86 relative to gear housing 78and bracket 90. In particular, bearing 148 is received within thirdportion 154 of gear housing 78, and bearing 144 is received within anopening 95 formed in end wall 96 of bracket 90.

Referring to FIGS. 12-16, outer screw assembly 120 of primary clutch 50includes a neck portion 128 and a threaded screw portion 127. Neckportion 128 extends through an opening 97 formed in end wall 96 ofbracket 90 (see FIG. 10). An outer bearing support 184 is rotatablycoupled to neck portion 128 via bearing assembly 183 and is fixedlycoupled to an end 71 of shaft 70. As such, shaft 70 and outer bearingsupport 184 rotate together independently from outer screw assembly 120.In the illustrated embodiment, end 71 of shaft 70 is press fit intoouter bearing support 184. End 71 further includes a circumferentialchannel 73 that engages an inner ridge 189 of outer bearing support 184(see FIG. 14). End 71 of shaft 70 may also be fastened to outer bearingsupport 184 with an adhesive or other suitable fastener.

Inner screw assembly 122 includes a plate portion 186 and a threadedscrew portion 188 positioned radially inwardly from plate portion 186.An L-shaped wall 185 is illustratively coupled between plate portion 186and screw portion 188 forming a radial gap 187 between screw portion 188and wall 185. Screw portion 188 includes outer threads 196 that matewith inner threads 129 of screw portion 127 of outer screw assembly 120.Screw portion 127 of outer screw assembly 120 is received within gap 187formed in inner screw assembly 122 (see FIGS. 14-16). An o-ring seal 192positioned radially inside of wall 185 is configured to abut screwportion 127 of outer screw assembly 120. Plate portion 186 of innerscrew assembly 122 includes flanges 124 having apertures 125 (see FIGS.12 and 13) that slidably receive posts 92 of bracket 90 (see FIGS. 8 and9). Plate portion 186 further includes slots 194 circumferentiallyspaced near the outer perimeter of plate portion 186.

Still referring to FIGS. 12-16, a sliding assembly of primary clutch 50includes a bushing assembly 172, a sliding support 200, and a bearingassembly 190 positioned between bushing assembly 172 and inner screwassembly 122. Bushing assembly 172 of primary clutch 50 includes a neckportion 176 that receives shaft 70 therethrough and a plurality offlanges 174 that couple to circumferentially spaced seats 202 ofmoveable sheave 102. A plurality of fasteners 173, illustratively screws173, are received by corresponding apertures of flanges 174 and seats202 to couple bushing assembly 172 to sheave 102. A bushing 178positioned within neck portion 176 engages shaft 70 and supports theoutboard end of moveable sheave 102. Shaft 70 is configured to rotateinside of bushing 178 at engine idle (when primary clutch 50 isdisengaged) and to rotate with bushing 178 when primary clutch 50 isengaged. Bushing 178 is configured to provide a low-friction surfacethat slides along shaft 70 during movement of sheave 102. Bushing 178may alternatively be a needle bearing.

Neck portion 176 of bushing assembly 172 is rotatably coupled to screwportion 188 of inner screw assembly 122 via bearing assembly 190positioned within screw portion 188. A collar 182 and a toothed lockwasher 180 are coupled to neck portion 176 extending through screwportion 188 (see FIGS. 14-16). Lock washer 180 illustratively includesan inner tab 181 (see FIG. 12) that engages a corresponding slot 177(see FIG. 12) in the outer surface of neck portion 176 such that lockwasher 180 rotates with bushing assembly 172. Collar 182 is threadedonto neck portion 176 and is rotatably fixed in place on neck portion176 with tabbed lock washer 180. Accordingly, bushing assembly 172,sheaves 100, 102, collar 182, washer 180, and outer bearing support 184are configured to rotate with shaft 70, while outer screw assembly 120and inner screw assembly 122 do not rotate with shaft 70. Bushingassembly 172 is configured to slide axially along shaft 70 via bearing178.

Sliding support 200 is coupled to sheaves 100, 102 to provide a slidinginterface for moveable sheave 102 relative to stationary sheave 100. Asillustrated in FIGS. 14-16, sliding support 200 includes a tube portion216 and a plate portion 214 coupled to and substantially perpendicularto tube portion 216. In one embodiment, plate portion 214 and tubeportion 216 are molded together, although plate and tube portions 214,216 may be coupled together with a fastener or by other suitablecoupling means. Plate and tube portions 214, 216 each rotate withsheaves 100, 102 and shaft 70. A pair of seals 220 a, 220 b and a clutch218 positioned between seals 220 a, 220 b are coupled between tubeportion 216 and shaft 70. Clutch 218 is illustratively a one-way clutch218 that free-wheels during vehicle idle and that locks tube portion 216to shaft 70 during engine braking. As such, one-way clutch 218 acts as abearing between tube portion 216 and shaft 70 during idling conditionsand locks tube portion 216 to shaft 70 when CVT 48 is being drivenfaster than engine 42 (i.e., when belt 54 and clutch 50 work tooverdrive engine 42 of FIG. 2).

As illustrated in FIG. 12, plate portion 214 includes a plurality ofsliding couplers 206 that are circumferentially spaced around the outerdiameter of plate portion 214. In the illustrated embodiment, the outerdiameter of plate portion 214 is nearly the same as the outer diameterof moveable sheave 102 such that couplers 206 of plate portion 214 areimmediately adjacent an inner cylindrical wall 203 of sheave 102.Couplers 206 are illustratively clips 206 that are configured toslidingly receive corresponding sliding members or ridges 204 that arecircumferentially spaced around inner wall 203 of moveable sheave 102.Ridges 204 extend radially inward from and substantially perpendicularto cylindrical inner wall 203. Ridges 204 illustratively include aradial width and a radial height that is substantially greater than theradial width. As illustrated in FIG. 17, a low-friction liner 208 ispositioned in each clip 206 to engage the sliding surface of ridges 204.In one embodiment, liner 208 is a low-friction composite or plasticmaterial, such as polyether ether ketone (PEEK), polyimide-based plastic(e.g. Vespel), or nylon, for example, with additives to reduce friction.As illustrated in FIGS. 14-16, a cylindrical bearing or bushing 222 andan o-ring seal 224 are positioned between moveable sheave 102 and tubeportion 216 to locate sheave 102 radially onto tube portion 216. Bushing222 provides a low friction sliding surface for sheave 102 relative totube portion 216. In one embodiment, grease is provided in theinterfaces between ridges 204 and clips 206 and between bushing 222 andtube portion 216 to reduce sliding friction.

Moveable sheave 102 is configured to slide relative to sliding support200 along ridges 204 of FIG. 12. In one embodiment, the sliding frictionbetween sheave 102 and sliding support 200 is minimized with the slidinginterface between couplers 206 and ridges 204 being near the outerdiameter of moveable sheave 102. In the illustrated embodiment, theouter diameter of moveable sheave 102 is large relative to the outerdiameters of shaft 70 and tube portion 216. In one embodiment, the outerdiameter of moveable sheave 102 is at least three times greater than theouter diameters of shaft 70 and tube portion 216.

As illustrated in FIGS. 14-16, bearing assemblies 183 and 190 are eachpositioned outside of the outer profile of moveable sheave 102. Inparticular, referring to FIG. 14, bearing assemblies 183, 190 arepositioned axially outside of the end of sheave 102 lying in plane 198.As such, bearing assemblies 183, 190 are axially spaced apart from thesliding interfaces formed with couplers 206 and ridges 204 and withbushing 222 and tube portion 216. In one embodiment, bearing assemblies183, 190 include angular contact bearings, although other suitablebearings may be used. Neck portion 176 of bushing assembly 172 is alsoillustratively positioned outside of the outer profile of moveablesheave 102, as illustrated in FIG. 14.

In operation, the actuation of gear drive 86 by motor 76 (see FIG. 10)is configured to modulate the gear ratio provided by primary clutch 50.Referring to FIG. 10, the output of motor 76 is transferred throughreduction gear 130 to main gear drive 86 to thereby rotate outer screwassembly 120 (see FIG. 8) of primary clutch 50. Outer screw assembly 120is stationary axially and rotates due to the rotation of main gear drive86 independent of a rotation of shaft 70. Referring to FIGS. 8 and 14,rotation of outer screw assembly 120 in a first direction unscrewsthreaded screw portion 188 of inner screw assembly 122 from threadedscrew portion 127 of outer screw assembly 120, thereby causing innerscrew assembly 122 to slide axially along posts 92 towards stationarysheave 100 while remaining rotationally stationary.

Referring to FIG. 14, the axial movement of inner screw assembly 122provides a thrust force against moveable sheave 102 via bushing assembly172 to move sheave 102 towards stationary sheave 100. As describedherein, bushing assembly 172 rotates within the rotationally stationaryinner screw assembly 122 via bearing assembly 190. As such, the thrustforce provided by inner screw assembly 122 is applied to bushingassembly 172 through bearing assembly 190. Similarly, rotation of outerscrew assembly 120 in a second, opposite direction causes inner screwassembly 122 to move axially away from stationary sheave 100 along posts92 (see FIG. 8) and to apply a pulling force on bushing assembly 172 andmoveable sheave 102 through bearing assembly 190. Bearing assemblies183, 190 provide axial movement of inner screw assembly 122, bushingassembly 172, and sheave 102 relative to shaft 70 that is independentfrom the rotational movement of shaft 70, sheaves 100, 102, slidingsupport 200, and bushing assembly 172. In the illustrated embodiment,the range of axial motion of inner screw assembly 122 relative to outerscrew assembly 120 defines the maximum and minimum gear ratios providedwith primary clutch 50, although other limit stops may be provided.

As illustrated in FIGS. 18 and 19, a clutch assembly 170 is coupled toshaft 70 to serve as a starting or launch clutch for primary clutch 50.Clutch assembly 170 is illustratively a dry centrifugal clutch 170integrated into primary clutch 50. Clutch assembly 170 is configured tobe positioned external to the engine case 43 (see FIG. 2) of engine 42.As such, clutch assembly 170 is not integrated with the engine case 43of engine 42 and is therefore not positioned in the engine oil. Rather,clutch assembly 170 is positioned outside of the engine case 43 and iscoupled to the output shaft 44 of engine 42 to operate as a dry startingclutch for primary clutch 50. As such, clutch assembly 170 is removablefrom engine 42 by pulling the clutch assembly 170 from shaft 44.

In assembly, clutch assembly 170 is positioned in an interior 209 ofprimary clutch 50 (see FIG. 19). Clutch assembly 170 includes an endplate 232 coupled to shaft 70 and having a plurality of posts 234. Inthe illustrated embodiment, shaft 70 and end plate 232 are integrallyformed, although shaft 70 may be coupled to end plate 232 using afastener or press-fit configuration. As illustrated in FIG. 14, shaft 70includes substantially cylindrical outer and inner surfaces 226, 228,respectively. Inner surface 228 forms a hollow interior region 229 ofshaft 70. Outer and inner surfaces 226, 228 illustratively taper fromend plate 232 towards end 71. The outer surface of shaft 70 furtherincludes a step 88 such that the diameter of the portion of shaft 70received by bushing assembly 172 and outer bearing support 184 issmaller than the diameter of the portion of shaft 70 positioned in tubeportion 216 of sliding support 200. In the illustrated embodiment, theoutput shaft 44 of engine 42 (see FIG. 2) is received by interior region229 of shaft 70 to drive rotation of clutch assembly 170. As such,clutch assembly 170 and shaft 70 rotate with engine 42.

Referring to FIGS. 18 and 19, clutch assembly 170 further includes shoesor arms 238 pivotally mounted to posts 234 via fasteners 240. Arms 238each include an aperture 236 that receives a corresponding post 234 ofend plate 232. Fasteners 240 illustratively include bolts and washers.Each arm 238 includes a friction pad 230 coupled to the outercircumferential surface of each arm 238. A spring 242 is coupled betweenadjacent arms 238 at seats 244 to bias arms 238 into spaced relationwith each other.

In the illustrated embodiment, clutch assembly 170 is disengaged fromprimary clutch 50 when engine 42 (see FIG. 2) is at or below engine idlespeed. As the engine speed and the corresponding rotational speed ofclutch assembly 170 increases, the centrifugal force acting on arms 238overcomes the biasing force of springs 242 and causes ends 246 of arms238 to swing radially outward, thereby forcing friction pads 230 intoengagement with an inner friction surface 210 (see FIG. 13) ofstationary sheave 100. The engagement of clutch assembly 170 withstationary sheave 100 transfers torque to sliding support 200 andmoveable sheave 102. As such, sheaves 100, 102, sliding support 200, andbushing assembly 172 all rotate with shaft 70. When the rotational speedof shaft 70 decreases to a threshold speed, the reduced centrifugalforce causes arms 238 to move radially inward away from surface 210 ofsheave 100. As such, clutch assembly 170 disengages primary clutch 50.Stationary sheave 100 illustratively includes a plurality ofcircumferentially spaced cooling fins 212 configured to reduce the heatgenerated by the engagement of clutch assembly 170.

In the illustrated embodiment, upon removing cover 61 and bracket 90from mounting bracket 62 (see FIG. 5), a disengaged centrifugal startingclutch 170 allows primary clutch 50 to be pulled off shaft 70 as oneassembled unit. Belt 54 (see FIG. 2) may be removed and/or replaced uponremoving primary clutch 50 from shaft 70. Further, actuator assembly 80(see FIGS. 9 and 10) remains coupled to mounting bracket 62 when primaryclutch 50 is removed from shaft 70 such that the gears of actuatorassembly 80 (e.g. reduction gear 130) are not required to be removed andreset or recalibrated. In one embodiment, primary clutch 50 and belt 54are removable from shaft 70 without removing main gear drive 86 (seeFIG. 5).

Centrifugal starting clutch 170 serves to separate the shifting functionof primary clutch 50 from the engagement function of the primary clutch50. In particular, the shifting function is performed by the primaryclutch 50 via CVT control logic 35 of controller 36 (see FIG. 2), whilethe engagement of primary clutch 50 is controlled by starting clutch170. As such, controller 36 is not required to control the engagement ofprimary clutch 50 because starting clutch 170 automatically engagesprimary clutch 50 upon reaching a predetermined rotational speed.

In an alternative embodiment, primary clutch 50 may be configured tooperate without a starting clutch 170. For example, in this embodiment,primary clutch 50 of CVT 48 is directly coupled to the output of engine42. When vehicle 10 is at idle or not running, CVT control logic 35positions moveable sheave 102 away from stationary sheave 100 such thatbelt 54 is positioned radially inward towards shaft 70, as illustratedin FIG. 6. In one embodiment, CVT control logic 35 positions sheave 102at a maximum open position when engine 42 is idling or not running suchthat moveable sheave 102 does not contact belt 54. In one embodiment,sheave 102 is disengaged from belt 54 during shifting ofsub-transmission 56 (see FIG. 2). As such, secondary clutch 52 isrotating at a zero or minimal speed upon shifting sub-transmission 56.Engagement of sheave 102 and belt 54 is initiated upon engine drivingtorque being requested, e.g. upon throttle request by an operator. Inanother embodiment, sheave 102 is moved into engagement with belt 54after sub-transmission 56 is shifted out of neutral and into gear. Inanother embodiment, moveable sheave 102 is spring-loaded away from belt54 during engine idle, and the shifting of sub-transmission 56 into gearmechanically causes sheave 102 to move back into engagement with belt54.

In one embodiment, CVT control logic 35 of FIG. 2 provides functionalityfor spike load reduction of the drive train by automatically shiftingCVT 48 (i.e., adjust primary clutch 50) upon detection of vehicle 10being airborne. For example, when vehicle 10 of FIG. 1 is airborne,wheels 24 may accelerate rapidly due to the wheels 24 losing contactwith the ground while the throttle operator 116 (see FIG. 2) is stillengaged by the operator. When the wheels 24 again make contact with theground upon vehicle 10 landing, the wheel speed may decelerate abruptly,possibly leading to damaged or stressed components of the CVT 48 andother drive train components. CVT control logic 35 initiates spike loadcontrol upon detection of vehicle 10 being airborne to slow drive trainacceleration (e.g., the acceleration of final drive 58) of the airbornevehicle 10. In one embodiment, CVT control logic 35 slows the rate atwhich CVT 48 upshifts during spike load control. In one embodiment, CVTcontrol logic 35 stops upshifting of CVT 48 at least momentarily duringspike load control or downshifts CVT 48 to a lower gear ratio. As such,the drive train acceleration of vehicle 10 is slowed before vehicle 10returns to the ground, and the inertial loading on CVT 48 and otherdrive train components (e.g. sub-transmission 56, final drive 58, etc.)upon vehicle 10 landing is reduced or minimized.

In one embodiment, CVT control logic 35 automatically adjusts the gearratio of CVT 48 of the airborne vehicle 10 such that the wheel speed iscontrolled to approach the wheel speed detected immediately prior tovehicle 10 becoming airborne. For example, CVT control logic 35determines a wheel speed of vehicle 10 immediately prior to vehicle 10becoming airborne or during a transition of vehicle 10 from the groundedstate to the airborne state. The determined wheel speed is set as thetarget speed, and CVT control logic 35 adjusts CVT 48 upon detection ofthe airborne state to control the wheel speed to return towards thetarget speed. In one embodiment, CVT control logic 35 adjusts CVT 48until the wheel speed reaches the target speed or until the vehicle 10returns to ground. As such, in one embodiment CVT control logic 35adjusts CVT 48 such that the wheel speed of vehicle 10 upon vehicle 10returning to the ground is substantially the same as the detected wheelspeed immediately prior to vehicle 10 becoming airborne.

In one embodiment, controller 36 determines that vehicle 10 is airborneupon detection of a sudden acceleration in drive train components. Forexample, controller 36 may detect the sudden acceleration based onfeedback from a wheel speed sensor, engine speed sensor, transmissionspeed sensor, or other suitable speed sensor on the drive train ofvehicle 10. In the illustrated embodiment, controller 36 continuouslymonitors the angular acceleration of the drive train by measuring thespeed of one of the shafts of CVT 48 or sub-transmission 56 with a speedsensor 59. Vehicle 10 is determined to be airborne when the accelerationin wheel speed or drive train speed exceeds the design specifications ofvehicle 10. For example, vehicle 10 has a maximum wheel accelerationbased on available torque from engine 42, the frictional force from theground, the weight of vehicle 10, and other design limits. When themonitored drive train components accelerate at a faster rate thanvehicle 10 is capable under normal operating conditions (i.e., whenwheels 24 are in contact with the ground), controller 36 determines thatwheels 24 have lost contact with the ground. One or more predeterminedacceleration limits are stored at memory 39 (FIG. 2) that correspond tothe design limits of vehicle 10 to trigger the spike load control. Uponvehicle 10 returning to ground, controller 36 detects the grounded stateof vehicle 10 and resumes normal control of CVT 48. In one embodiment,controller 36 detects the grounded state based on a detected compressionof the vehicle suspension.

In one embodiment, the spike load reduction feature of CVT control logic35 works in conjunction with the electronic throttle control system(e.g., engine control logic 34) to reduce drive train acceleration(i.e., by reducing the throttle opening, etc.) upon detection of anairborne condition, as described in U.S. patent application Ser. No.13/153,037, filed on Jun. 3, 2011 and entitled “Electronic ThrottleControl,” the disclosure of which is incorporated herein by reference.The CVT 48 control and electronic throttle control are used together toreduce the acceleration of the drive train when vehicle 10 is airborne.In some operating conditions, a high or increasing throttle demand isprovided with throttle operator 116 while vehicle 10 is airborne. In oneembodiment, the engine 42 continues to rev due to the high throttledemand until a rev limit of the engine 42 is reached. In the exemplaryvehicle 10 having electronic throttle control, airflow to the engine 42is automatically restricted upon detection of the airborne condition toreduce engine power and to reduce the likelihood of reaching the revlimit.

Controller 36 may detect an airborne condition of vehicle 10 using othermethods, such as by detecting the compression distance or height of asuspension system (e.g. front suspension assembly 26 of FIG. 1 and/orrear suspension) of vehicle 10 with a suspension height sensor and/or bymonitoring engine torque and power, as described in the referenced U.S.patent application Ser. No. 13/153,037. For example, vehicle 10 includesone or more suspension sensors 119 (FIG. 2) configured to measure theheight or longitudinal compression of vehicle suspension (e.g., shocks).With vehicle 10 positioned on the ground, the weight of vehicle 10causes the suspension to compress to a first height. With tires 22 aand/or tires 22 b (FIG. 1) airborne, the weight of vehicle 10 is removedfrom the suspension system and the suspension decompresses or extends toa second unloaded height. Based on feedback from sensors 119 (FIG. 2),controller 36 determines that vehicle 10 is airborne upon the suspensionextending past the first height or to the second unloaded height. In oneembodiment, the suspension must be extended for a threshold amount oftime before controller 36 determines that vehicle 10 is airborne. In oneembodiment, controller 36 uses the detected shock height in conjunctionwith the detected wheel speed acceleration to determine that vehicle 10is airborne.

In one embodiment, CVT 48 further includes a planetary gear assembly toprovide an infinitely variable transmission system. In one embodiment,the planetary gear assembly consists of a ring gear, several planetarygears coupled to a carrier, and a sun gear. The ring gear is drivendirectly off the output of engine 42 via a gear or chain. The planetarygears and the carrier are connected to and driven by the secondaryclutch 52. The sun gear serves as the output of CVT 48 connected to thesub-transmission 56. Based on the gear ratios of the planetary gearassembly, the combined CVT 48 and planetary gear assembly are configuredto provide both positive and negative speeds (forward and reverse) byvarying the gear ratio of the CVT 48. In one embodiment, the hydrostaticmode provided with controller 36 and described herein is implemented ina CVT 48 having a planetary gear assembly.

In one embodiment, CVT 48 is electro-hydraulically actuated, asillustrated with the exemplary electro-hydraulic circuit 278 of FIG. 20.In the illustrated embodiment of FIG. 20, primary clutch 50 of CVT 48 isactuated by electro-hydraulic circuit 278 rather than by actuatorassembly 80 of FIGS. 10 and 11. Circuit 278 may also be configured tocontrol secondary clutch 52. Electro-hydraulic circuit 278illustratively includes a hydraulic circuit 282 and an electric circuit284. Controller 36 illustratively receives analog inputs 250, digitalinputs 252, and CAN inputs 254. Exemplary analog and digital inputs 250,252 include hydraulic system pressure sensors, a clutch position sensor(e.g. sensor 290 of FIG. 20), a servo valve position sensor, and othersensors detecting various parameters of vehicle 10. Exemplary CAN inputs254 include an engine speed sensor, throttle position sensor, vehiclespeed sensor, vehicle operating mode sensor, and other CAN based sensorsthat detect various parameters of vehicle 10. Controller 36 isconfigured to control an electric motor 262 of electric circuit 284 anda pump 264 and a servo valve 272 of hydraulic circuit 282 based oninputs 250, 252, 254.

A motor driver 256 is configured to control the power provided to motor262 based on control signals from controller 36. Alternatively, a relaymay be provided in place of motor driver 256 that is selectivelyactuated by controller 36 to provide fixed power to motor 262. Motor 262may be any motor type suitable for driving pump 264. In the illustratedembodiment, motor 262 is a DC electric motor. A voltage supply 261,illustratively 12 VDC, is provided to motor 262, and the speed of motor262 is controlled by controller 36 via motor driver 256. An output 263of motor 262 drives pump 264. In the illustrated embodiment, pump 264 isa variable displacement pump 264. A pump control unit 258 of controller36 modulates the displacement of pump 264 to control hydraulic pressureof hydraulic circuit 282 based on inputs 250, 252, 254. Pump 264 mayalternatively be a fixed displacement pump.

A hydraulic accumulator 268 stores pressurized hydraulic fluid to assistpump 264 and motor 262 with meeting the pressure demands of hydrauliccircuit 282. For example, accumulator 268 is configured to achieverequired pressure demands of hydraulic circuit 282 during peak shiftrates of CVT 48. As such, the likelihood of spike loads being induced onthe electric circuit 284 during peak shift rates of CVT 48 is reduced. Apressure relief valve 270 is provided to maintain the pressure onhydraulic line 288 below a predetermined maximum threshold pressure.Pressure relief valve 270, pump 264, and servo valve 272 are coupled toa hydraulic return reservoir 280.

Servo valve 272 regulates the flow of hydraulic fluid from line 288 toactuator 274 to adjust the position of moveable sheave 102. Servo valve272 is illustratively a three-way electro-hydraulic servo valve 272controlled by a servo valve driver 260 of controller 36. Servo valvedriver 260 of controller 36 controls servo valve 272 based on inputs250, 252, 254. Actuator 274, illustratively a linear hydraulic actuator,includes a piston 275 coupled to moveable sheave 102 via a rotarybearing 276. In one embodiment, rotary bearing 276 is a flanged bearingor a face bearing, although another suitable bearing 276 may beprovided. In one embodiment, actuator 274 is coupled to chassis 15 ofvehicle 10 (see FIG. 1), and moveable sheave 102 rotates about piston275 of actuator 274 and moves axially relative to actuator 274 viabearing 276. Servo valve 272 is coupled to actuator 274 via hydrauliclines 286. In one embodiment, lines 286 are small diameter, highpressure hydraulic lines 286. By regulating the fluid flow to actuator274 with servo valve 272, linear displacement of actuator 274 isadjusted to cause corresponding axial adjustment of moveable sheave 102.

In one embodiment, electric circuit 284 and hydraulic circuit 282 arepositioned on vehicle 10 (see FIG. 1) away from CVT 48, and actuator 274is positioned immediately adjacent or within housing 60 (see FIG. 4) ofCVT 48. As such, hydraulic lines 286 are routed from servo valve 272 tothe actuator 274 positioned near CVT 48. For example, electric circuit284 and hydraulic circuit 282 may be placed beneath hood 32 and/or seats18 a, 18 b (see FIG. 1), and CVT 48 and actuator 274 may be positionedtowards the rear end 14 of vehicle 10 beneath engine cover 19 (see FIG.1). As such, the actuation components (i.e. actuator 274) of themoveable sheave(s) 102 of CVT 48 occupy a small space at the location ofCVT 48 while some or all of the remaining components ofelectro-hydraulic circuit 278 are positioned elsewhere on vehicle 10.

In one embodiment, the pressure applied to moveable sheave 102 viaactuator 274 is modulated to achieve a desired gear ratio of CVT 48and/or a desired pinch force on belt 54. As illustrated in FIG. 20, aposition sensor 290 is configured to detect the linear position ofmoveable sheave 102 and provide a corresponding signal to controller 36with the detected position data. As such, the position of sheave 102 maybe monitored during operation. In one embodiment, controller 36implements a fail-safe mode in the control of moveable sheave 102. Inparticular, when a system failure or signal loss is detected bycontroller 36, moveable sheave 102 is positioned to a maximum low ratioor open position such that the pinch force on belt 54 is minimized orremoved, as described herein. An exemplary system failure is when no orinadequate hydraulic pressure in hydraulic circuit 282 is detected withinputs 250, 252.

Referring again to drive system 40 of FIG. 2, the electronicallycontrolled clutch 50, 52 of CVT 48 is configured to move to a homeposition prior to or upon shutting down vehicle 10. For example, thecontrolled clutch 50, 52 moves to its fully open position (see FIG. 8,for example) or to its fully closed position (see FIG. 9, for example).In the illustrated embodiment, upon vehicle shutdown, moveable sheave102 of primary clutch 50 moves to its furthest open position, asillustrated in FIG. 8. As such, moveable sheave 102 is positioned awayfrom and out of contact with belt 54 prior to vehicle 10 being started,thereby reducing the likelihood of vehicle 10 accelerating upon startingengine 42. In one embodiment, for an electronically controlled secondaryclutch 52, the moveable sheave (not shown) of secondary clutch 52 ismoved to its furthest closed position upon or prior to vehicle shutdown.

Referring to FIG. 2, vehicle 10 includes a system battery 118 (e.g. 12VDC) configured to provide power for starting vehicle 10 and to provideperipheral power to vehicle 10 during operation. The system battery 118provides power to actuator assembly 80 to move moveable sheave 102 tothe home position upon vehicle 10 being shutdown or being stopped andshifted into neutral. Primary clutch 50 of CVT 48 is also configured toreturn to a home position upon vehicle 10 suffering an abrupt powerloss, as described herein with reference to FIGS. 21-23.

In another embodiment, vehicle 10 does not have a system battery 118.For example, vehicle 10 may include a mechanical rope and recoilassembly that is pulled by an operator to start engine 42. Inparticular, the pull of the rope by an operator rotates a powergenerator that starts engine 42 of vehicle 10, and the power generatorwhen driven by rotating engine 42 provides peripheral power to theelectronic components of vehicle 10 during operation. See, for example,generator 304 of FIG. 22. As such, power from a system battery 118 isnot available to move primary clutch 50 to its home position whilevehicle 10 is shut down. In this embodiment, primary clutch 50 is movedto its home position prior to shutting down vehicle 10 using the powerprovided with generator 304, as described herein.

Referring to FIG. 21, an exemplary control strategy 350 is illustratedfor moving primary clutch 50 to its home position in a vehicle 10 nothaving a system battery 118. Control strategy 350 is illustrativelyimplemented by controller 36 of FIG. 2. At block 352, an indicator (e.g.audible or visual) is provided on vehicle 10 upon moving the vehicle keyto the ON position to indicate to the operator if primary clutch 50 isat its home position. In one embodiment, the indicator, such as a light,for example, is powered by a small, low-voltage battery. The indicatormay alternatively be mechanically linked to the CVT 48 to detect theposition of clutch 50. If primary clutch 50 is at its home position,engine 42 is started by the operator, as illustrated at blocks 354, 356,and 358. For example, an operator may start engine 42 via a manual startsystem, such as a rope/recoil assembly or kick start assembly. In oneembodiment, actuation of the manual start system is blocked when primaryclutch 50 is not at its home position at block 352.

Upon an operator commanding engine 42 to stop at block 360 (e.g. turningthe vehicle key to OFF), primary clutch 50 automatically returns to itshome position at block 362 prior to controller 36 allowing engine 42 topower down. In particular, controller 36 executes a shut down sequenceat block 362 wherein controller 36 retains engine power despite theoperator commanding shutdown, moves sheave 102 of primary clutch 50 toits home position by routing power from generator 304 (FIG. 22) toactuator assembly 80, and then allows engine 42 to shut down (block364). At block 366, engine 42 shuts down. Accordingly, primary clutch 50is at the home position before engine 42 shuts down such that vehicle 10may be properly started up again at a future time without having toreset clutch 50.

If primary clutch 50 is not at its home position at block 352, primaryclutch 50 must be moved to its home position prior to starting vehicle10, as illustrated at blocks 368, 370, and 372. For example, clutch 50may require a reset when vehicle 10 abruptly loses power beforecontroller 36 is able to reset clutch 50 to its home position. Primaryclutch 50 may be reset manually or via automated control. In the manualreset of block 374, an operator removes cover 61 (see FIG. 5) of CVT 48and manually resets moveable sheave 102 to its home position by turningouter screw assembly 120 (see FIG. 5). In the automated reset of block376, vehicle 10 includes an auxiliary power connector 330 for connectingvehicle 10 to an external power supply 322 (e.g. 12 VDC), as illustratedin the exemplary control system 300 of FIG. 22. In one embodiment, theexternal power supplied through auxiliary power connector 330 is routedto controller 36 to power the controller 36, as illustrated in FIG. 22.Upon detecting the presence of external power, controller 36 movesprimary clutch 50 to its home position via actuator assembly 80. Inanother embodiment, power provided through auxiliary power connector 330is routed to a switch 324 or other tool (e.g., diagnostic tool) that anoperator actuates to return primary clutch 50 to the home position. Forexample, switch 324 includes a closed position that allows current topass to actuator 80 to move clutch 50 to the home position and an openposition that blocks current from actuator 80. An operator actuatesswitch 324 to control the delivery of power to actuator 80 and thus tocontrol the position of clutch 50. In one embodiment, switch 324 is usedin conjunction with controller 36 (as illustrated in FIG. 22) such thatswitch 324 enables and disables the automated return of clutch 50 to thehome position controlled by controller 36. Alternatively, switch 324 maybypass controller 36 such that switch 324 controls the delivery of powerto actuator 80 and the position of clutch 50 without controller 36. Atblock 378, if primary clutch 50 is at the home position, the operator isable to start engine 42 at blocks 354 and 356. If primary clutch 50 isnot at the home position at block 378, the process returns to block 372for additional manual or automated movement of clutch 50.

Referring to FIG. 22, the exemplary control system 300 is furtherconfigured to provide a fail safe for returning clutch to the homeposition upon sudden power loss in a vehicle 10 not having a systembattery 318 (FIG. 2). Control system 300 illustratively includes amicrocontroller 302 that controls a switch 320 to selectively routepower stored at a capacitor 316 to controller 36. Microcontroller 302includes a processor and a memory accessible by the processor andcontaining software with instructions for monitoring vehicle power 306,detecting power interruption, and controlling switch 320.Microcontroller 302 and controller 36 may alternatively be integrated ina single controller that includes logic that performs the functionsdescribed herein of both controllers 302, 36. Generator 304, driven byengine 42 (FIG. 2) during vehicle operation, provides vehicle power 306(illustratively 12 VDC) for controller 36, microcontroller 306, andother vehicle components and for charging capacitor 316 during vehicleoperation. Capacitor 316 may alternatively be charged by external powersupply 322 via auxiliary connection 330. Capacitor 316 is charged duringvehicle operation while electrically decoupled from actuator 80 (i.e.,with switch 320 open). A fuse 308 and a diode 310, illustratively aZener diode 310, are provided in series between vehicle 306 andcontrollers 302, 36 to provide reverse voltage protection. A diode 312,illustratively a transient voltage suppression diode 312, is coupledbetween the output of diode 310 and ground to provide over-voltageprotection for controllers 302, 36. A resistor 314 is provided forcharging capacitor 316.

Microcontroller 302 is configured to close switch 320 upon detection ofa power loss at vehicle power 306. For example, upon vehicle 10 abruptlylosing power and generator 304 shutting down, microcontroller 302 sensesthe drop or loss of vehicle power 306 and closes switch 320. In oneembodiment, microcontroller 302 includes a power source (e.g.,capacitor) that powers microcontroller 302 after a vehicle power loss sothat microcontroller 302 can close switch 320 after the power loss. Withswitch 320 closed, power stored at capacitor 316 is routed to controller36 for moving primary clutch 50 of CVT 48 to the home position. In oneembodiment, capacitor 316 is an ultra-capacitor. Capacitor 316 mayinclude another suitable energy storage device 316, such as a lithiumion battery or another lightweight battery that is smaller than atypical vehicle system battery 318 (FIG. 2).

Referring to FIG. 23, an exemplary control strategy 400 is illustratedfor control system 300 of FIG. 22. With engine running at block 402, anoperator signals a vehicle shutdown at block 404, and the normalshutdown process for vehicle 10 is performed at block 406. For example,the shutdown process illustrated in blocks 360, 362, 364, and 366 ofFIG. 21 and described herein is performed at block 406 of FIG. 23. If anabrupt power loss is detected by controller 302 (FIG. 22) at block 410,controller 302 determines at block 412 if capacitor 316 is charged andfunctioning properly. If controller 302 determines capacitor 316 is notfunctioning properly, switch 320 is not closed and primary clutch 50 ismoved to its home position at block 418 manually or via auxiliary powerconnection 320, as described with blocks 374 and 376 of FIG. 21. Ifcapacitor 316 is functioning properly at block 412, microcontroller 302closes switch 320 to route power from capacitor 316 to controller 36 atblock 414. Controller 36 uses the power from capacitor 316 to driveactuator assembly 80 to move primary clutch 50 of CVT 48 to its homeposition. At block 416, controller 36 (or microcontroller 302)determines if clutch 50 is at its home position based on feedback from aposition sensor (e.g. sensor 290 of FIG. 20). If clutch 50 is at itshome position, the shutdown of vehicle 10 is determined to be proper atblock 408. If clutch 50 is not at its home position at block 416,process 400 proceeds to block 418 for a manual (or automated) reset ofclutch 50, as described herein with blocks 374, 376 of FIG. 21. In oneembodiment, capacitor 316 is sized to contain enough energy for movingclutch 50 to its home position based on a predetermined worst-case setof initial operating conditions where power interruptions could occur.

In another embodiment, vehicle 10 includes a mechanical return systemfor automatically positioning primary clutch 50 at the home positionupon system power being removed. For example, in this embodiment, amechanical spring/linkage system is coupled to moveable sheave 102 (seeFIG. 5) of primary clutch 50 to position primary clutch 50 in its homeposition upon vehicle 10 being powered down. When power is returned tovehicle 10, controller 36 operates normally to control primary clutch50, as described herein.

CVT control logic 35 (FIG. 2) is operative to implement traction controlupon detecting a loss of tire traction. In particular, controller 36determines a loss of traction has occurred upon detecting a high rate ofchange of the speed of one or more wheels 24 (FIG. 1), i.e., when therate of change of speed exceeds a threshold rate. For example, one ormore wheels 24 may accelerate or decelerate rapidly upon loss oftraction, indicating that the wheel(s) 24 have spun out or have lockedup. In one embodiment, upon detection of traction loss, CVT controllogic 35 inhibits shifting of CVT 48 and holds the gear ratio of CVT 48substantially constant until determining that traction has beenregained. By holding the gear ratio constant, undesirable shifting ofCVT 48 due to the rapid change in speed of wheels 24 during tractionloss is avoided. In one embodiment, CVT control logic 35 determines thattraction has been regained based on the monitored speed of wheels 24.

Controller 36 provides a plurality of operating modes for CVT 48selectable with one or more mode selection devices 113 (FIG. 2).Exemplary operating modes include automatic, manual mimic, andhydrostatic modes. Further, controller 36 provides a cruise control modeselectable with a cruise switch. In the cruise control mode, at leastone of the engine throttle position and the gear ratio of CVT 48 is heldconstant to hold the vehicle speed at a target vehicle speed. In oneembodiment, the vehicle speed upon selection of the cruise control modeby an operator is set as the target vehicle speed, although the targetvehicle speed may be entered by an operator via a user interface ofvehicle 10. In one embodiment, the throttle position of engine 42 islocked or held constant by engine control logic 34 in cruise mode tohold the engine torque substantially constant, and the gear ratio of CVT48 is varied by CVT control logic 35 based on vehicle speed feedback tomaintain the target vehicle speed. In another embodiment, the gear ratioof CVT 48 is held constant during cruise control while the throttleposition of engine 42 is varied to maintain the target vehicle speed.Alternatively, both the throttle position and the gear ratio of CVT 48may be held substantially constant or may be simultaneously adjusted tocontrol vehicle speed to the target speed.

In the hydrostatic mode, the engine speed and the gear ratio of CVT 48are controlled independently by an operator. For example, the enginespeed is selected (e.g. with throttle operator 116 or another suitableoperator input device) based on a particular use or application ofvehicle 10, i.e., for powering vehicle implements with a power take-off,for charging system capacity, etc. The gear ratio of CVT 48 is selectedby an operator with a separate input device, such as a pedal lever, orjoystick. In one embodiment, the hydrostatic operating mode isselectable only when vehicle 10 is substantially stopped or when vehicle10 is moving below a threshold vehicle speed (e.g., 5 mph).

CVT 48 is controlled by CVT control logic 35 to operate in either themanual mimic mode or the automatic mode based on an operator's selectionof the manual or automatic mode via mode selection device 113. In theautomatic mode, CVT control logic 35 actively adjusts CVT 48 across acontinuum of available gear ratios based on the detected engine speed,the position of throttle operator 116, and a target engine speed, asdescribed herein. In the manual mimic mode, CVT control logic 35 shiftsCVT 48 between a plurality of discrete gear ratios to simulate atraditional manual or automatic transmission. In particular, primaryclutch 50 is moved to predetermined fixed positions based on an operatorshift input (e.g., input from shifter 55 of FIG. 2), and each positionprovides a different discrete gear ratio. For example, in a firstindicated gear, primary clutch 50 is moved to a first predeterminedposition providing a first gear ratio. When a second indicated gear isselected with shifter 55, primary clutch 50 is moved to a secondpredetermined position providing a second gear ratio higher than thefirst gear ratio.

In the illustrated embodiment, an operator inputs a shift command tocontroller 36 to initiate the discrete gear shift in the manual mimicmode. In one example, the actuation of shifter 55 (FIG. 2) signals tocontroller 36 to shift the discrete gear ratio of CVT 48. Exemplaryshifters 55 include paddles, switches, knobs, shift lever 29 (FIG. 1),or other suitable shift devices. In one embodiment, an upshifter 55 anda downshifter 55 are mounted adjacent steering wheel 28 (FIG. 1) suchthat an operator may shift gears in manual mimic mode without having tocompletely remove their hand from the steering wheel 28. In oneembodiment, primary clutch 50 is moved to five or six predeterminedpositions across the displacement range of primary clutch 50 to providefive or six discrete gear ratios of CVT 48, although fewer or additionalgear ratios may be provided. In another embodiment, CVT control logic 35is operative to shift CVT 48 automatically between each predefineddiscrete gear ratio.

In the automatic mode of operation, CVT control logic 35 continuallycalculates a target engine speed during vehicle operation based on thedetected throttle operator position. Based on the calculated targetengine speed and the current engine speed, CVT control logic 35proactively shifts CVT 48 to a gear ratio that will cause engine controllogic 34 (FIG. 2) to control engine 42 to the calculated target enginespeed, as described below. An operator is able to adjust the clutchshift profile of CVT 48, and thus the target engine speed correspondingto throttle input, based on input via input device 111 to adjust thedesired performance and/or fuel economy of vehicle 10.

Referring to FIG. 24, a flow diagram 450 of an exemplary methodperformed by CVT control logic 35 is illustrated for calculating atarget position of primary clutch 50 in the automatic mode of operation.Reference is made to CVT 48 of FIGS. 2-19 throughout the description ofFIG. 24. Flow diagram 450 illustrates a control loop that is executed byCVT control logic 35 to continually adjust the target clutch position(i.e., the target gear ratio of CVT 48) during vehicle operation basedon the detected engine speed, the throttle demand, and the target enginespeed, as described herein. Based on the target clutch position, CVTcontrol logic 35 is further operative to provide a control signaldelivered to actuator assembly 80 to move primary clutch 50 to thetarget clutch position, as described herein with respect to flow diagram500 of FIG. 29.

At block 452, CVT control logic 35 detects the current engine speedbased on feedback from an engine speed sensor 59. At block 454, CVTcontrol logic 35 determines if the position of primary clutch 50 iscurrently within operating range limits based on position sensor 114(FIG. 5). In particular, if moveable sheave 102 is positioned (or iscommanded by actuator assembly 80 to be positioned) beyond itspredetermined limits of travel along shaft 70, CVT control logic 35enters a protection mode at block 456 by controlling motor 76 accordingto the maximum voltage curve illustrated in FIG. 30 and describedherein. In one embodiment, the protection mode includes disabling motor76 and holding sheave 102 at the nearest maximum position within thetravel range limits. Upon generating a clutch command signal to moveclutch 50 to another position within the range limits, motor 76 isenabled and controlled to move clutch 50 accordingly. As such, thelikelihood of damaging clutch components and/or burning out motor 76 isreduced. If the current clutch position is within the travel limits atblock 454, CVT control logic 35 proceeds to block 462.

At block 462, CVT control logic 35 calculates a preliminary targetclutch position (i.e., position of moveable sheave 102 along shaft 70)based on the current engine speed detected at block 452, a target enginespeed calculated at block 460, and the current clutch position. In theillustrated embodiment, the target engine speed is calculated at block460 based on a target engine speed map 480, illustrated in FIG. 27 anddescribed below. CVT control logic 35 receives user inputs at block 458and calculates the target engine speed based on the user inputs. In theillustrated embodiment, the user inputs received at block 458 are thethrottle operator position (e.g., pedal position) and a clutch controlvariable (i.e., a calibration factor used in clutch control). Thethrottle operator position is provided with the position sensor ofthrottle operator 116 (FIG. 2). The clutch control variable, alsoreferred to herein as the “K factor,” is illustratively selected withinput device 111 (FIG. 2). In particular, input device 111 ismanipulated by an operator to select the value of the clutch controlvariable provided as input to CVT control logic 35 for modifying theclutch shift profile of CVT 48. For example, based on the clutch controlvariable, CVT control logic 35 implements operating characteristics ofvehicle 10 ranging from an economic operation with maximized fueleconomy to a sport operation with maximized vehicle performance.

Referring to FIG. 25, an exemplary input device 111 is illustrated as arotary knob 111. In one embodiment, rotary knob 111 is coupled to apotentiometer or other suitable sensing device for providing positionfeedback to CVT control logic 35. The magnitude (e.g., voltagemagnitude) of the signal provided with knob 111 to CVT control logic 35corresponds to the position of knob 111. Each position of knob 111corresponds to a different value of the clutch control variable used inthe calculation of the target engine speed at block 460 of FIG. 24.Rotary knob 111 is illustratively mounted to front dashboard 31 ofvehicle 10. A vehicle performance indication 430 and a shift intensityindication 432 are illustratively provided adjacent rotary knob 111. Inthe automatic mode of operation, the vehicle performance indication 430illustrates the vehicle performance corresponding to the position ofknob 111. In the manual mimic mode of operation, the shift intensityindication 432 illustrates the shift quality or shift intensity selectedbased on the position of knob 111 (described further herein). Rotaryknob 111 includes a pointer or selection tab 434 that points to thedesired performance level (automatic mode) or the desired shiftintensity (manual mode) provided on respective indications 430, 432. Tomaximize average fuel economy in the automatic mode, rotary knob 111 isrotated fully counterclockwise such that tab 434 points towards the“economy” mode illustrated on indication 430. To maximize vehicleperformance (e.g., acceleration, torque, etc.) in the automatic mode,rotary knob 111 is rotated fully clockwise such that tab 434 points tothe “sport” mode illustrated on indication 430. As the position of knob111 is rotated from the economy indication to the sport indication, theperformance of vehicle 10 corresponding to the throttle demand increaseswhile the average fuel economy decreases.

In the illustrated embodiment, the clutch control variable selected withrotary knob 111 has normalized values ranging from −1.0 to +1.0, andeach value corresponds to a desired performance of vehicle 10. Referringto FIG. 26, a graph 475 illustrates a curve 476 representing exemplaryvalues of the clutch control variable (i.e., K-factor values) on they-axis that correspond to a voltage magnitude or position of rotary knob111 on the x-axis. Curve 476 is illustratively a polynomial regressioncurve that is fit to several K-factor values, although other suitablecurves may be provided depending on the configuration of knob 111. AK-factor value of −1.0 (point 477) corresponds to the economy modewherein rotary knob 111 of FIG. 25 is rotated fully counterclockwise. AK-factor value of +1.0 (point 478) corresponds to the sport mode whereinrotary knob 111 of FIG. 25 is rotated fully clockwise. IntermediateK-factor values between −1.0 and +1.0 correspond to differentperformance levels of vehicle 10 (and thus different rotationalpositions of knob 111). For example, as the K-factor value increasesfrom −1.0 to +1.0, the performance of vehicle 10 associated withthrottle demand increases while the average fuel economy decreases. AK-factor value of 0.5 (point 479) illustratively corresponds to a normalmode of operation wherein the average fuel economy and vehicleperformance are both at average or unmodified levels. In the illustratedembodiment, the clutch control variable may be set to any intermediatevalue continuously through the range between −1.0 and +1.0. Othersuitable mappings of the voltage from rotary knob 111, or from anotherinput device 111, to the clutch control variable may be provided.

In another embodiment, shifters 55 (FIG. 2) are used to adjust the valueof the clutch control variable in the automatic mode (block 458 of FIG.24). For example, each actuation of the upshifter 55 or downshifter 55increments the clutch control variable up or down respectively to adjustthe clutch shift profile of CVT 48 incrementally. As such, a discretenumber of available clutch shift profiles are selectable with shifters55 ranging from the peak economy mode to the peak performance mode.

As described above, CVT control logic 35 calculates the target enginespeed at block 460 (FIG. 24) based on the clutch control variableselected with rotary knob 111 (or with shifters 55) and the throttledemand. Referring to FIG. 27, an exemplary engine target map 480 isshown illustrating target engine speeds (in rpm) corresponding to aparticular throttle demand, i.e., a position of throttle operator 116.Depending on the selected value of the clutch control variable, adifferent target engine speed curve is calculated and/or selected by CVTcontrol logic 35. Based on the selected target engine speed curve, CVTcontrol logic 35 determines at block 460 of FIG. 24 a target enginespeed that corresponds to the detected throttle operator position.

The x-axis of FIG. 27 illustrates the entire range of throttle operatorpositions from 0% (throttle operator 116 fully released) to 100%(throttle operator 116 fully depressed or actuated by the operator). They-axis of FIG. 27 illustrates the entire range of target engine speeds.Line 490 represents an exemplary maximum engine speed of engine 42 ofabout 8300 rpm. Line 492 illustrates the maximum throttle operatorposition of 100%. Curve 482 of FIG. 27 identifies target engine speedscorresponding to the throttle demand when the K factor is equal to zero.Curve 482 illustrates a linear relationship between the throttle demandand engine speed. Curve 484 corresponds to a K factor of −1.0 andidentifies the target engine speeds for the maximized economy mode.Curve 486 corresponds to a K factor of +1.0 and identifies the targetengine speeds for the maximized sport mode. Another exemplary curve 488corresponds to a K factor of +0.75 and illustrates target engine speedsfor a mode having increased but not maximized performancecharacteristics. In one embodiment, each curve includes an associatedarray of points (e.g., 20 points, etc.), and linear interpolation isused to calculate the target engine speed curve from the array ofpoints.

In one embodiment, CVT control logic 35 calculates a target engine speedcurve in real-time during vehicle operation upon detecting the selectedvalue of the clutch control variable. In particular, a group of pointsfrom at least one target engine speed curve of map 480 is stored inmemory 39 of controller 36. For example, an array of 20 points fromlinear curve 482 is stored in memory 39. Based on the K-factor valueselected with input device 111, an offset or distance from each point inthe stored array is calculated and stored in an offset array having thesame size as the point array for curve 482. Each offset may beproportional to the K-factor value. Based on the offset array and thepoint array for curve 482, CVT control logic 35 determines a new arrayof points that define a new target engine speed curve. In oneembodiment, linear interpolation is used to calculate the target enginespeed curve from the determined new set of points. In anotherembodiment, multiple target engine speed curves may be stored in alookup table in memory 39, and CVT control logic 35 may retrieve andutilize a target engine speed curve that corresponds to the selectedvalue of the clutch control variable. Only four curves are shown in map480 of FIG. 27 for illustrative purposes. However, CVT control logic 35is operative to calculate a different curve for each K-factor value. Inan embodiment wherein the magnitude of the signal from input device 111is continuously adjustable, the range of engine speed curves that may becalculated is therefore also continuous.

Referring again to the method of FIG. 24, CVT control logic 35calculates the target engine speed at block 460 by calculating the curvebased on the K-factor and determining the target engine speedcorresponding to the throttle demand. With the target engine speedcalculated, CVT control logic 35 then determines the target position ofprimary clutch 50 of CVT 48 that would allow vehicle 10 to achieve thattarget engine speed, i.e., the clutch position that would cause enginecontrol logic 34 to control engine 42 from the current engine speed tothe target engine speed. As such, CVT control logic 35 calculates apreliminary target clutch position at block 462 based on the detectedengine speed (block 452), the determined target engine speed, and thecurrent clutch position. In the illustrated embodiment, CVT controllogic 35 calculates the preliminary clutch position at block 462 using aPID (proportional-integral-derivative) control loop with the currentengine speed, the target engine speed, and the current clutch positionas the input variables. In an alternative embodiment, vehicle speed isfurther considered by CVT control logic 35 in the calculation of thetarget clutch position.

At block 468, CVT control logic 35 manipulates the preliminary targetclutch position at block 470 based on the current vehicle accelerationdetected at block 464. In one embodiment, CVT control logic 35 detectsthe current acceleration based on speed feedback from a ground speedsensor 59 (FIG. 2). CVT control logic 35 calculates a target clutchvelocity at block 466 based on the detected vehicle acceleration andmodifies the preliminary target clutch position at block 468 based onthe target clutch velocity. The target clutch velocity is the rate atwhich clutch 50 (i.e., moveable sheave 102) is to be moved to its newposition, i.e., the rate of change of the gear ratio of CVT 48. Bymodifying the target clutch position based on the vehicle acceleration,CVT control logic 35 implements feedforward control of clutch 50 bypredicting where the clutch 50 needs to be moved to in order for theengine control logic 34 to react and control engine 42 to the targetengine speed identified at block 460. As such, the gear ratio of CVT 48is proactively shifted based on the vehicle acceleration such thatengine 42 achieves the target engine speed. For example, if the targetengine speed is higher than the current engine speed of vehicle 10, andvehicle 10 is accelerating rapidly, CVT control logic 35 calculates aclutch velocity configured to shift CVT 48 quickly to reduce thelikelihood that engine control logic 34 overshoots the target enginespeed. The target clutch velocity determined at block 466 thus serves asa manipulation variable to modify the preliminary target clutch positioncalculated at block 462.

In one embodiment, the target velocity of clutch 50 is determined basedon a lookup table or other predetermined mapping. FIG. 28 illustrates anexemplary graph 494 that maps the vehicle acceleration values (x-axis)to corresponding clutch velocities (y-axis). In the exemplary mapping ofFIG. 28, the target clutch velocity increases gradually around region495 as the vehicle acceleration increases. As the vehicle accelerationcontinues to increase, the target clutch velocity increases more rapidlyaround region 496 before increasing exponentially around region 497. Assuch, the higher the vehicle acceleration, the more quickly the targetclutch velocity increases. The mapping of FIG. 28 illustrates anexemplary clutch control strategy, and other suitable target clutchvelocities may be selected for a given vehicle acceleration.

Upon calculating the target clutch position at block 472, CVT controllogic 35 applies travel range limits of CVT 48 at block 474. Inparticular, if the target clutch position is outside of predeterminedlimits of travel along shaft 70, CVT control logic 35 resets the targetclutch position to the nearest maximum position before proceeding toblock 474. If the target clutch position is within the travel limits atblock 472, CVT control logic 35 proceeds to block 474. At block 474, CVTcontrol logic 35 sends the calculated target clutch position to theposition control algorithm described in FIG. 29.

Referring to FIG. 29, a flow diagram 500 of an exemplary methodperformed by CVT control logic 35 is illustrated for generating acontrol signal for adjusting CVT 48 to the target clutch position. Thecontrol signal is provided to actuator assembly 80 during vehicleoperation to control CVT 48 based on the calculated target clutchposition. At block 502, CVT control logic 35 detects the currentposition of primary clutch 50 based on position sensor 114 (FIG. 5).Blocks 504 and 506 are identical to blocks 454 and 456 of FIG. 24. Inparticular, if the current or commanded clutch position is out of range,CVT control logic 35 enters a protection mode, as described above. Atblock 510, CVT control logic 35 enters a PID loop with the detectedcurrent clutch position and the target clutch position (block 508) asinput variables. In the automatic mode, the target clutch position ofblock 508 is calculated with the method of FIG. 24, as described above.In the manual mimic mode, the target clutch position is determined basedon the discrete gear ratio selected by the operator via shifters 55(FIG. 2). The output of the PID loop of block 510 is the calculateddirection (block 512) and magnitude (514) of clutch movement. Inparticular, at block 512 the rotational direction of motor 76 and thusthe axial direction of moveable sheave 102 are determined. At block 514,the magnitude (e.g., voltage or current magnitude) of the clutch controlsignal to be provided to motor 76 is determined based on the comparisonof the current clutch position and the target clutch position. At block516, CVT control logic 35 applies the travel range limits of CVT 48 tothe target clutch position, as described herein with respect to block472 of FIG. 24. At block 518, CVT control logic 35 transfers the clutchcontrol signal to motor 76 (or to a motor driver of motor 76) forcontrolling the gear ratio of CVT 48. In one embodiment, the clutchcontrol signal defines a percentage of pulse-width modulation to beapplied to motor 76 as well as the direction of rotation of motor 76.

In one embodiment, the travel range limits implemented at block 472 ofFIG. 24 and block 516 of FIG. 29 are based on the maximum appliedvoltage limits illustrated in graph 530 of FIG. 30. Graph 530illustrates an exemplary maximum applied voltage (y-axis) as a functionof the position of clutch 50 (x-axis). Moveable sheave 102 of primaryclutch 50 has a minimum position limit and a maximum position limitdefined by the physical limits of travel, i.e., hard stops, of moveablesheave 102. The minimum position limit corresponds to a fully closedclutch 50 wherein moveable sheave 102 is positioned against fixed sheave100. The maximum position limit corresponds to a fully open clutchwherein screw portion 188 of inner screw assembly 122 is fully receivedwithin screw portion 127 of outer screw assembly 120 (FIG. 14). Clutch50 further includes a target operating range illustratively definedbetween positions X₁ and X₂ of graph 530 that is a smaller travel rangethan the range defined by the physical limits of travel. In the targetoperating range, the voltage applied to motor 76 is limited to a maximumlimit 534, as illustrated with line 532. Between end position X₁ of thetarget operating range and the minimum physical limit, the maximumapplied voltage is ramped down along line 536 from limit 534 to a zerovoltage when clutch 50 reaches position Y₁. Similarly, between endposition X₂ of the target operating range and the maximum physicallimit, the maximum applied voltage is ramped down along line 538 fromlimit 534 to a zero voltage when clutch 50 reaches position Y₂. Voltageis removed from motor 76 at clutch positions Y₁ and Y₂ before moveablesheave 102 can reach the respective minimum and maximum travel limits.As such, when the position of clutch 50 is outside the target operatingrange, the applied voltage is gradually reduced, illustrativelylinearly, and is removed entirely from motor 76 prior to clutch 50reaching the minimum/maximum positions to reduce the likelihood ofdriving moveable sheave 102 into the physical hard stops of CVT 48.

In the manual mimic mode of operation of CVT 48, controller 36 (FIG. 2)is operative to interrupt engine torque during the transition betweendiscrete gear ratios. Torque interruption includes reducing or removingengine torque temporarily during the gear shift. Such torqueinterruption serves to simulate the inertia shift or shift feelassociated with shifting gears in a traditional sequential manual orautomatic transmission. In one embodiment, the torque interruptionfurther serves to improve the shift speed provided by motor 76 byreducing the axial loads on primary clutch 50 due to engine torqueduring the shift transient. In the illustrated embodiment, the torqueinterruption is implemented during an upshift, although torqueinterruption may also be implemented during downshifts. In oneembodiment, CVT control logic 35 detects the shift request from shifter55 and sends a message or command to engine control logic 34 requestingthe torque interruption. In the exemplary embodiment, torque reductionis implemented by engine control logic 34 by temporarily inhibiting orsuppressing engine ignition during the transition between discrete gearratios (i.e., inhibiting or cutting spark from one or more spark plugsof engine 42). Other suitable methods for interrupting engine torqueduring shift transients may be implemented, such as, for example, byretarding ignition timing, reducing the throttle or air intake, reducingor cutting fuel injection, etc. In one embodiment, vehicle or drivelinebrakes may be temporarily applied during shift transients to reducevehicle torque.

Referring to FIG. 31, an exemplary torque interruption profile 550calculated by CVT control logic 35 is illustrated with the percentage ofthe maximum available engine torque on the y-axis and time on thex-axis. At time T₀, the torque interruption request is received byengine control logic 34 from CVT control logic 35 upon an operatorrequesting a gear shift with one of shifters 55. An onset delay betweentimes T₀ and T₁ serves to delay the onset of the torque reduction. Attime T₁, implementation of the torque reduction begins. In oneembodiment, voltage is applied to motor 76 at about time T₁ such thatprimary clutch 50 begins moving to the new discrete position at abouttime T₁. Between times T₁ and T₂, the torque reduction is ramped up toreduce the available engine torque from Torq_(max) to Torq_(min). In theillustrated embodiment, Torq_(max) is equal to the maximum availabletorque (i.e., 100% of available engine torque). In the illustratedembodiment, Torq_(min) is a fraction of the maximum available torque,such as, for example, 30% or 40% of the maximum available torque. Anysuitable Torq_(min) may be provided that is less than Torq_(max).Between times T₂ and T₃, full torque reduction is implemented for apredetermined duration, i.e., the available torque is held atTorq_(min). At time T₃, the full torque reduction is ramped back down toincrease the available torque from Torq_(min) to Torq_(max) betweentimes T₃ and T₄. At time T₄, the torque reduction ends, and enginecontrol logic 34 allows full available engine torque. In the illustratedembodiment, the available engine torque is linearly decreased betweentimes T₁ and T2 and linearly increased between times T₃ and T₄, althoughother reduction profiles may be implemented. In one embodiment, theprimary clutch 50 completes movement to the new discrete gear positionat about time T₄ or between times T₃ and T₄.

The torque interruption request provided by CVT control logic 35identifies several parameters that define torque interruption profile550. In the illustrated embodiment, the onset delay (time from T₀ andT₁), the magnitude (i.e., difference between Torq_(min) and Torq_(max)),the duration (time from T₁ and T₄), and the ramp rates (time from T₁ toT₂ and from T₃ to T₄) of the torque reduction are all included in thetorque interruption request to define torque interruption profile 550.The intensity of each upshift is dependent on the values of theseparameters.

In the illustrated embodiment, torque interruption profile 550 of FIG.31 is modified by an operator with input device 111 to adjust the shiftintensity. In particular, referring again to FIG. 25, the rotationalposition of knob 111 in the manual mimic mode corresponds to a desiredshift intensity or quality. The shift intensity is continuouslyadjustable between “soft” intensity with minimized torque interruption(tab 434 fully counterclockwise) to “firm” shift intensity withmaximized torque interruption (tab 434 full clockwise), as illustratedwith indication 432 of FIG. 25. In the illustrated embodiment, themagnitude and/or the duration of the torque interruption are modifiedbased on the position of knob 111. In some embodiments, the onset delayis also adjustable with input device 111. Any other suitable parametersof the torque reduction profile 550 may be adjusted with input device111 and/or with other operator input. As such, CVT control logic 35 isoperative to generate the torque interruption request based on theposition of knob 111.

In one embodiment, the torque interruption profile 550 is furtherdependent on the current discrete gear ratio and the discrete gear ratiorequested with the shifter 55. For example, a shift from the firstindicated gear to the second indicated gear in manual mimic mode may becontrolled by controller 36 to have a greater shift intensity than ashift from the fourth indicated gear to the fifth indicated gear. Othersuitable adjustments of the torque interruption profile may beimplemented based on the gear transition.

In the exemplary embodiment, five indicated gears (first through fifth)are provided in the manual mode, i.e., an operator may select withshifters 55 between five indicated gears. Fewer or additional indicatedgears may be provided. In the illustrated embodiment, the indicatedfirst gear has a gear ratio that is variable across a low range, and theother indicated gears (second through fifth) have fixed discrete gearratios. In particular, in the first indicated gear the actual gear ratioof CVT 48 is continuously adjusted between a minimum low gear ratio anda higher gear ratio. As such, when the indicated first gear is selectedby an operator in the manual mode, CVT control logic 35 continuouslyvaries the gear ratio across a predetermined low range (similar tovariable clutch operation in the automatic mode). Once an operatorselects the indicated second gear with shifter 55, CVT control logic 35shifts CVT 48 to a discrete gear ratio that is higher than the gearratios provided in the low range of the indicated first gear. In oneembodiment, such variable clutch operation in the indicated first gearreduces the speed at which an operator must shift between the first andsecond indicated gears while still providing the low-end power availablein low gear ratios.

For example, FIG. 32 illustrates an exemplary shifting scheme for astandard six-speed manual sequential transmission. Each indicated gearon the x-axis (i.e., selected by an operator with a shift device)corresponds to a single fixed, physical gear ratio on the y-axis.Indicated sixth gear of FIG. 32 corresponds to vehicle overdrive, forexample. FIG. 33 illustrates an exemplary shifting scheme provided withthe manual mimic mode of CVT 48. When the indicated first gear isselected (with shifters 55), CVT control logic 35 controls the gearratio to vary between a minimum low gear ratio 570 (e.g., 3.0 ratio) anda maximum low gear ratio 572 (e.g., 2.1 ratio). As such, the control ofCVT 48 in the indicated first gear of manual mode is similar to thecontrol in automatic mode over the low clutch travel range. Each ofindicated gears two through five of the exemplary manual mode of FIG. 33has a corresponding single fixed gear ratio. In the illustratedembodiment, gear ratios 570, 572 of the indicated first gear correspondto the first and second gear ratios of the exemplary standard shiftingscheme of FIG. 32.

CVT control logic 35 further includes shift protection logic operativeto monitor vehicle operating characteristics before allowing an upshiftor a downshift in the manual operating mode. In particular, CVT controllogic 35 determines whether it will execute a shift request based on themonitored engine speed. For each indicated gear in the manual mimicmode, a low engine speed threshold and a high engine speed threshold arestored in memory 39. For a downshift request, CVT control logic 35 doesnot implement the downshift if the detected engine speed is above thehigh engine speed threshold that is associated with the currentindicated gear. For an upshift request, CVT control logic 35 does notimplement the upshift if the detected engine speed is below the lowengine speed threshold that is associated with the current indicatedgear. In one embodiment, the high engine speed threshold for eachindicated gear is set to reduce the likelihood that a downshift causesthe engine 42 to overspeed or redline. In one embodiment, the low enginespeed threshold for each indicated gear is set to reduce the likelihoodthat an upshift causes the engine 42 to fall below a minimum idealoperating speed while the vehicle is moving. As such, the likelihoodthat the starting clutch 170 disengages or slips relative to primaryclutch 50 during vehicle operation is reduced, for example. Further, thelow engine speed threshold further ensures that CVT 48 is at a minimumclutch ratio (i.e., the indicated first gear) when vehicle 10 comes to astop. In the illustrated embodiment, CVT control logic 35 does notconsider vehicle speed when determining whether a shift request isallowed during normal vehicle operation. Because vehicle speed is notconsidered, the protection control is implemented with the same low andhigh engine speed thresholds regardless of the final drive ratio (e.g.,low or high gear) provided with sub-transmission 56 (FIG. 2). In oneembodiment, upon a detected failure of the engine speed signal, thevehicle speed is considered by control logic 35 to determine whether toexecute the shift request.

In one embodiment, CVT control logic 35 forces a downshift in the manualmimic mode when the detected engine speed drops below a predeterminedthreshold speed. Each indicated gear other than first gear has anassociated predetermined threshold speed that dictates when a downshiftwill be automatically executed by CVT control logic 35. For eachindicated gear, the predetermined threshold speed for forcing adownshift is lower than the low threshold speed for preventing executionof an upshift request described above.

CVT control logic 35 is operative to allow an operator to switch betweenautomatic and manual modes on the fly during movement of vehicle 10. Anoperator may request a change between the automatic and manual modeswith mode selection device 113 at any time during vehicle operation. CVTcontrol logic 35 monitors operating parameters of vehicle 10 todetermine whether the mode change request is safe for execution.Referring to FIG. 34, a flow diagram 600 of an exemplary mode changeoperation of CVT control logic 35 is illustrated. At block 602, CVTcontrol logic 35 determines the current mode of operation (automatic ormanual). At block 606, CVT control logic 35 detects a mode changerequest from mode selection device 113 (block 604). Upon detection ofthe mode change request, CVT control logic 35 implements one of two modechange strategies—manual to automatic or automatic to manual. For amanual to automatic mode change request (block 608), CVT control logic35 determines a target clutch position based on the throttle demand, thecurrent engine speed, and the target engine speed, as described hereinwith respect to FIG. 24. CVT control logic 35 then compares the targetclutch position to the current fixed clutch position of the manual mode,and calculates the transition from the current fixed clutch position tothe target clutch position. CVT control logic 35 then switches from themanual mode to the automatic mode at block 610 and implements thetransition.

For an automatic to manual mode change request (block 612), CVT controllogic 35 determines the next lowest discrete gear ratio of the manualmode at block 614 as compared with the current clutch position. Theclutch position corresponding to the next lowest discrete gear ratio ispre-selected and loaded into the gear state before the mode transitionoccurs. At block 616, CVT control logic 35 determines if the selecteddiscrete gear ratio is within predetermined limits based on the enginespeed. In particular, CVT control logic 35 calculates the distancebetween the current clutch position and the desired clutch positioncorresponding to the discrete gear selected at block 614. CVT controllogic 35 compares this distance to the total distance between thedesired clutch position (of the selected discrete gear) and the clutchposition of the next highest discrete gear above the selected lowerdiscrete gear. A high engine speed threshold is calculated based onthese parameters as follows:

$\begin{matrix}{{EngSpd}_{Threshold} = {{\frac{{ClutchPos}_{NextDiscrete} - {ClutchPos}_{Current}}{{ClutchPos}_{NextDiscrete} - {ClutchPos}_{Selected}}*2500} + 6000}} & (1)\end{matrix}$wherein EngSpd_(Threshold) is the engine speed threshold (in rpm),ClutchPos_(Current) is the current clutch position,ClutchPos_(NextDiscrete) is the clutch position of the next highestdiscrete gear above the lower discrete gear selected at block 614, andClutchPos_(Selected) is the clutch position of the discrete gearselected at block 614. In the exemplary equation (1), if the currentclutch position is far away from the position of the new target position(ClutchPos_(Selected)), the engine speed threshold is close to 6000 rpm.If the current clutch position is near the new target position(ClutchPos_(Selected)), the engine speed threshold approaches 8500 rpm.Other suitable engine speed thresholds may be provided.

At block 616, if the current engine speed is less than or equal toEngSpdThreshold, then the mode change is executed. If the current enginespeed is greater than EngSpd_(Threshold) at block 616, then the modechange is inhibited until the engine speed drops below the threshold. Assuch, CVT control logic 35 shifts down to the next lowest discrete gearratio when transitioning from automatic to manual modes. If at the timeof the mode request the gear ratio of CVT 48 in the automatic mode islower than the lowest discrete gear ratio in manual mode, CVT controllogic 35 upshifts CVT 48 to the indicated first gear of the manual mode.

CVT control logic 35 is further operative to monitor for slip ofstarting clutch 170 (FIG. 18) relative to primary clutch 50. CVT controllogic 35 compares the detected engine speed to the rotational speed ofprimary clutch 50 during operation of CVT 48. CVT control logic 35determines that starting clutch 170 is slipping relative to primaryclutch 50 based on the primary clutch speed deviating from the detectedengine speed. Upon the difference in engine speed and primary clutchspeed exceeding a predetermined threshold, CVT control logic 35 issues awarning (visual and/or audible) to the operator that the starting clutch170 needs inspection and/or servicing. The warning may be provided ondisplay 53 of FIG. 2, for example.

CVT control logic 35 is further operative to monitor for wear ordeterioration of CVT belt 54 (FIG. 6). Based on the position of primaryclutch 50 provided with position sensor 114, CVT control logic 35determines an expected gear ratio of CVT 48. CVT control logic 35measures the rotational speeds of primary and secondary clutches 50, 52to determine the actual gear ratio of CVT 48. If the actual gear ratiodeviates from the expected gear ratio by more than a threshold amount,CVT control logic 35 determines that belt 54 may be worn or faulty andmay be past its useful life. Accordingly, CVT control logic 35 issues awarning (e.g., via display 53) to the operator that the belt 54 needsinspection and/or servicing.

In one embodiment, primary clutch 50 is adjusted in the automatic modebased on engine speed according to a brake specific fuel consumption mapstored at memory 39 of controller 36. In particular, controller 36 isoperative to set engine speed operating points based on the brakespecific fuel consumption map to improve or maximize fuel economythroughout the operating range of engine 42. The engine speed operatingpoints are selected based on minimum specific fuel consumption as afunction of increasing power levels.

In one embodiment, other operating characteristics of vehicle 10 may beadjusted by controller 36 based on the K-factor provided with inputdevice 111. In one exemplary embodiment, the stiffness of the vehiclesuspension is adjusted based on the mode selected and the vehicleperformance selected. In one embodiment, a stiffer suspension improvesvehicle handling while diminishing the smoothness of the ride. Forexample, in the manual mode, the stiffness of the suspension of vehicle10 is increased to improve vehicle handling. In the automatic mode, thestiffness of the suspension of vehicle 10 is increased proportionally asrotary knob 111 (FIG. 25) is turned clockwise towards the improved sportperformance. Other suitable operating characteristics of vehicle 10 maybe adjusted based on the clutch profile selected with input device 111,such as, for example, power steering control, the enabled/disabledstatus of anti-lock brakes, the enabled/disabled status of tractioncontrol, the enabled/disabled status of rear differential lock, and theintrusion level of vehicle stability control.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

What is claimed is:
 1. A method of controlling a continuously variabletransmission of a vehicle carried out by at least one control unit, thevehicle including an engine operative to drive the continuously variabletransmission, the method including: determining a speed of the engine ofthe vehicle; detecting a throttle parameter; determining a clutchcontrol variable based on an operator input device, the continuouslyvariable transmission of the vehicle including a first clutch and asecond clutch, the first clutch being moveable by an actuator tomodulate a gear ratio of the continuously variable transmission; whereinthe actuator is operated to move the first clutch from an initialposition to the target position calculating a target engine speed basedon the clutch control variable; detecting an acceleration rate of thevehicle; and calculating a target position of the first clutch of thecontinuously variable transmission based on the calculated target enginespeed, the detected acceleration rate of the vehicle, and the determinedspeed of the engine; determining a target velocity of the first clutchbased on the vehicle acceleration rate for a movement of the firstclutch from the initial position to the target position, wherein thecalculating the target position of the first clutch of the continuousvariable transmission is further based on the target velocity.
 2. Themethod of claim 1, further including calculating the target position ofthe first clutch of the continuously variable transmission regardless ofa speed of the vehicle.
 3. The method of claim 1, wherein calculatingthe target position of the first clutch of the continuously variabletransmission based on the calculated target engine speed, the detectedacceleration rate of the vehicle, and the determined speed of the engineoccurs during normal operation of the engine.
 4. The method of claim 1,further including adjusting the target engine speed upon detection of anadjustment of the clutch control variable with the operator inputdevice, wherein adjustment of the target engine speed is operative toadjust a performance level of the vehicle corresponding to the throttleparameter.
 5. The method of claim 4, wherein adjusting the performancelevel of the vehicle includes adjusting between a peak fuel economyperformance level and a peak engine torque performance level.
 6. Themethod of claim 1, wherein calculating the target engine speed includesaccessing a target engine speed map stored in memory of the at least onecontroller and determining the target engine speed associated with thethrottle parameter from the target engine speed map based on the clutchcontrol variable.
 7. The method of claim 1, wherein the target enginespeed is calculated further based on the throttle parameter.
 8. Themethod of claim 7, wherein the throttle parameter includes a throttledemand calculated by the at least one control unit based on a detectedposition of a throttle operator device.
 9. The method of claim 1,wherein the operator input device is moveable between a plurality ofpositions each corresponding to a different performance level of thevehicle, and wherein the clutch control variable is determined based onthe position of the operator input device.
 10. A vehicle including: achassis; a ground engaging mechanism configured to support the chassis;an engine supported by the chassis; a continuously variable transmissiondriven by the engine, the continuously variable transmission including afirst clutch, a second clutch, and a belt coupled to the first andsecond clutches, the first clutch being adjustable with an actuator tomodulate a gear ratio of the continuously variable transmission; athrottle valve configured to regulate a speed of the engine; at leastone controller including engine control logic operative to control aposition of the throttle valve and transmission control logic operativeto control a position of the first clutch of the continuously variabletransmission, the at least one controller being operative to detect anacceleration rate of the vehicle; an engine speed sensor incommunication with the at least one controller for detecting a speed ofthe engine; a throttle operator device moveable by an operator andincluding a position sensor in communication with the at least onecontroller, the position sensor being configured to detect a position ofthe throttle operator; and an operator input device in communicationwith the at least one controller configured to adjust a clutch controlvariable provided to the at least one controller, the transmissioncontrol logic being operative to calculate a target engine speed basedon the clutch control variable, the transmission control logic beingoperative to calculate a target position of the first clutch of thecontinuously variable transmission based on the target engine speed, thedetected acceleration rate of the vehicle, and the detected enginespeed; and the transmission control logic being operative to control theactuator to move the first clutch from an initial position to the targetposition, the transmission control logic further determining a targetvelocity of the first clutch based on the vehicle acceleration rate fora movement of the first clutch from the initial position to the targetposition, wherein the transmission control logic calculates the targetposition of the first clutch of the continuous variable transmissionfurther based on the target velocity.
 11. The vehicle of claim 10, thetransmission control logic being operative to calculate the targetposition of the first clutch regardless of a speed of the vehicle. 12.The vehicle of claim 10, the transmission control logic being furtheroperative to generate a control signal provided to the actuator toadjust the first clutch of the continuously variable transmission to thetarget position.
 13. The vehicle of claim 10, the transmission controllogic being further operative to adjust the target engine speedcorresponding to the position of the throttle operator device upondetection of an adjustment of the clutch control variable with theoperator input device, wherein adjustment of the target engine speed isoperative to adjust a performance level of the vehicle corresponding tothe position of the throttle operator device.
 14. The vehicle of claim13, wherein adjusting the performance level of the vehicle includesadjusting between a peak fuel economy performance level and a peakengine torque performance level.
 15. The vehicle of claim 10, whereinthe transmission control logic calculates the target engine speed byaccessing a target engine speed map stored in memory of the at least onecontroller and determining the target engine speed associated with theposition of the throttle operator device from the target engine speedmap based on the clutch control variable.
 16. The vehicle of claim 10,wherein the operator input device is moveable between a plurality ofpositions each corresponding to a different performance level of thevehicle, and wherein the clutch control variable is determined based onthe position of the operator input device.
 17. The vehicle of claim 10,wherein the target position of the first clutch corresponds to a targetgear ratio of the continuously variable transmission.